Saturday, September 21, 2019

Rock Creek Gold Placer - A Mine Frozen in Time

Introduction
1987 photo of the Rock Creek gold placer, South Pass. Near center of photo, some relatively fresh diggings
mark the location of the Gerald South placer (photo by the author).
When I moved to Wyoming, I did not become a cowboy. I got along fine with cowboys, but I just wasn't the cowboy type - didn't like horses, cowboy hats, or cowboy boots. Instead, I was into rocks and minerals, field boots, safari hats, and coyotes. 

We moved to Wyoming from New Mexico so I could work for the US Geological Survey. Then we moved from Casper to Laramie, where I went to work for the Wyoming Geological Survey. Over the years, I was employed as VP of US Exploration for DiamonEx Ltd and consulted on many gold, diamond and base metal deposits for companies, leading some to  mineral deposits. One of these deposits will soon become one of the largest gold mines in the world. 

I guess my fascination with mines developed during my college years, and in particular, I was fascinated by igneous and metamorphic rocks as well as diamond depositsgreenstone belts, gold, porphyry copper, and gemstones. I would likely still be working at the Wyoming Geological Survey (University of Wyoming), but during my last year in Laramie, I ended up working under two of the most corrupt politicians I've ever known - except maybe for Clinton (well, no I did not know the Clintons, thank goodness). So, I applied for early retirement and went off to work for DiamonEx Ltd, as well as consult for other mining companies. DiamonEx, Ltd, almost had a diamond mine in Colorado, but things fell apart with the 2008 stock market crash.

In 2015, RC Mineral and Rock, LLC hired me to consult on their Rock Creek gold placer at South Pass, Wyoming. I had an insatiable interest in South Pass beginning all the way back to when I started working for the Wyoming Geological Survey, and was hoping to one day get an opportunity to map the greenstone belt in its entirety. Less than half of the exposed greenstone belt had been mapped by Richard Bayley of the US Geological Survey, and I wanted to cover every inch of the ground in the greenstone belt as well as examine accessible old gold mines and the Atlantic City iron mine in the greenstone belt. So, in 1991, my treatise on the South Pass greenstone belt with a map of the belt was published (Hausel, 1991). I had a wonderful time, met many people I still call friends, accessed some of the old gold mines, and spent countless nights under the stars singing cowboy songs with the local coyotes.

Much of my early field work in Wyoming was devoted to diamond research.  I mapped the two largest diamond-bearing kimberlite districts in the US (Iron Mountain and State Line) and later mapped the largest lamproite field in North America (Leucite Hills). I extended my knowledge of diamond deposits while consulting for two different companies and searched for diamond deposits throughout the US and elsewhere. I worked for other diamond companies searching for diamond and/or deposits in California, Colorado, Kansas and Montana, but I could hardly wait to get started on South Pass, and other greenstone belt fragments in the Rattlesnake Hills, Seminoe Mountains, as well as the Copper Mountain supracrustal belt in the Owl Creek Mountains. I also examined many other potentially commercial gold deposits, such as in the Silver Crown district in the Laramie Mountains, and elsewhere in the US.

I was told by a couple of Directors at the Wyoming Geological Survey, and the Department Head of the UW Geology Department, that much of everything known about the Precambrian terrain in Wyoming, was due to my research, much like what Dr. Dave Love (RIP) did for Wyoming's basin geology and uranium deposits. It felt good to be standing in the same circle as Dr. Love - my good friend. 

I received a similar compliment from Dr. Sam Goldich at the Colorado School of Mines related to diamond deposits. Sam almost convinced by to spend time at CSM to do some isotopic geochemistry on the diamond deposits, but at the time, I was interested in mapping. But I wish I would have taken Sam up on his offer: Sam and I became friends  while working together on a International Geochemical Field Conference.

Mining districts and mineralized terrains of Wyoming (From Hausel and Hausel, 2011).
The diamond-bearing kimberlites in the State Line district were initially acquired by companies in the late 1970s and early 1980s, and gem-quality diamonds up to 28.3 carats in weight were recovered. During bulk sampling of the Kelsey Lake kimberlite, one diamond fragment was recovered from a larger diamond that was estimated to have originally been  about 90 carats (Howard Coopersmith, personal communication, 1996). 

So, in the early 1980s, mining companies had taken over much of the activity in the diamond districts freeing me to begin other research projects. The one that interested me the most was the South Pass greenstone belt at the southern tip of the Wind River Mountains where much of the geology and extent of gold mineralization was relatively unknown at the time. 

After beginning reconnaissance at South Pass in the 1980s, I was awarded a series of COGEOMAP grants from the US Geological Survey, which led me to a nearly decade of geological mapping of the 400 mi2 greenstone belt, its mines, and gold. Armed with a tent, topographic maps, Bruton compass, aerial photographs and a few pairs of boots, I began mapping accessible underground mines and the ground surface, and by the end of the project, had mapped eight 1:24,000 scale quadrangles (each quadrangle included approximately 48 mi2). These were compiled into a 1:48,000 scale map on the greenstone belt incorporated into a Report of Investigations published in 1991. 

South Pass Mining History
According to historical records, the first report of gold at South Pass was made by a trapper with the American Fur Company in 1842. The location of his discovery is believed to have been Strawberry Creek, east of Rock Creek. Several years later (1855), a group of 40 prospectors entered South Pass to follow up on the gold discovery and reported finding gold nearly everywhere. This was followed by a group of 9 prospectors who returned to the area in 1858, and commenced mining on Strawberry Creek. The decayed remains of their sluices were found in 1870.

While working at the Wyoming Geological Survey, I often led field
trips for the public, prospectors, and professional associations. Here,
I am talking to a public group just outside the old Atlantic City iron
mine at South Pass.
In 1861, another expedition to South Pass included a group of 52 prospectors who began mining Willow Creek (4 miles west of Strawberry Creek and 2 miles west of Rock Creek), when they were attacked by Indians and driven out. Two years later (1863), gold was  discovered on the Oregon Trail south of South Pass in the vicinity of Oregon Buttes. More than a century later, the US Geological Survey studied gold at Oregon Buttes and described one of the largest undeveloped gold anomalies in North America (Figure 1). 

In June 1867, a rich lode gold deposit was discovered along Willow Creek and the mine was named the Carissa. A short time later, the miners were attacked by Indians: three were killed and the rest driven out. The group returned in late July and in the winter of that year, more than 400 ounces of gold were recovered from the lode using only primitive hand tools. An additional four tons of high-grade ore was shipped to Springfield, Utah that yielded an incredible 1,400 ounces of gold!

Figure 1. Oregon Buttes viewed from geographical South Pass. The Oregon Buttes gold-paleoplacer forms
 much of the ridge in the sunlit area below Oregon Buttes. The US Geological Survey estimated the paleoplacer
 could host 28.5 million ounces of gold making it one of the largest undeveloped gold anomalies in North
 America. The source of the gold has not been identified but in all probability lies at depth beneath the cover of
 the younger South Pass and Wasatch Formations (photo by the author). In other words, it would appear from
 geological evidence, that a significant lode gold deposit occurs at depth within a buried portion of the South
 Pass greenstone belt.
Hostilities continued between miners and Indians forcing the US Army to establish Camp Stambaugh near the boom towns of Atlantic City and Miners Delight in 1870. But the Army had problems keeping recruits due to the many gold discoveries, which resulted in many soldiers deserting to search for gold. 

Figure 2. The Carissa lode (shear zone) at the surface is mineralized over a minimum width of 300 feet and
 likely as much as 1,000 feet. A case can be made that this shear structure continues 4 miles to the east to Rock
Creek where the gold-bearing structure is likely offset before continuing another 6 miles east to 
the edge of
the
  greenstone belt near Miners Delight.

Along this structure, periodic ore shoots occur that have considerable unprospected ground in-between ore
 shoots. The structure also continues a short distance west of the Carissa shaft where it disappears under
 geologically young sediments of the South Pass Formation and likely terminates against granitic rocks of the
 Louis Lake batholith (a potential source for some of the gold in the structure) (photo by the author). 
Based on limited sampling, drilling and extent of this deposit, it likely hosts over 
a million ounces of gold & potentially several million ounces. 
However, due to the lack of wisdom by the Wyoming legislature, the state
 purchased the property and quickly withdrew it from future mining, and ended up producing Wyoming's 
answer to Disneyland for the few dozen tourists that visit the mining park. For scale, note the geologist (Jon
 King) standing to the right of shear zone. Yes, keep looking, Jon is standing there.


By 1872, twelve stamp mills were reportedly operating in the greenstone belt and in 1878, the Army abandoned Camp Stambaugh and the Oregon Trail to the south had to be abandoned for a safer route further south due to increased Indian attacks. Hostilities ceased following the signing of the Treaty of Five Nations in 1882. 

Figure 3. Steve Gyorvary stands in the mined out portion of the Carissa lode on the 400-foot-level. This part of the high-grade lode was mined in the past and the empty space provides a nice perspective of the lode’s attitude. The lode stands nearly vertical and from this mine level, it continues upward to the surface. It also continues several hundred feet (potentially a few thousand feet) below this point. When the lode was mined, only the high-grade ore was profitable at low gold prices, and miners left an enormous, low-grade, resource in place. The low-grade ore is found in the mine ribs (walls) and could potentially occur over a 1000 foot width! During past operations, the mine produced more than 180,000 ounces of gold based on incomplete production records. But the un-mined deposit likely hosts considerably more gold than mined in the past (photo by the author)
In 1884, significant gold placer operations were proposed and the Granier ditch was constructed to haul water from Christina Lake (12 miles northwest) to South Pass. Startup of hydraulic operations did not occur until 1890. In 1891, 6,720 ounces were recovered.

Shear zones like the Carissa lode are important as these continue to feed gold into drainages in the greenstone belt. The shears are recognized by intensely folded and faulted structures containing broken (brecciated) rock, mylonite, strong lineation and foliation with quartz fillings and boudins (Figure 2). Several shear zones (lodes) have been identified that trend between South Pass City to Atlantic City to Miners Delight and many more are likely buried by alluvium and eluvium. There is also evidence at the Carissa mine that the shears continue to great depth: so there is a continuous source for detrital gold for placers in the region.

Gold from very small area on Rock Creek at the Stout mine (1987).
At the Carissa, past drilling by Consolidated McKinney Resources identified a highly anomalous, 80-foot-wide zone at depth. Assays of drill core ranged from 0.03 to 2.54 ounces per ton gold (the shear envelop was not tested). This mineralized structure was also intersected to depths as great as 930 feet. Anaconda Minerals Company reported their drill holes on the property interested a high grade ore zone of widths of 2.3 to 16.1 feet that yielded 0.11 to 0.36 opt Au to depths of 700 feet. 

In summary, there is ample supply of gold for placers downslope from the known lodes, and the lodes have been eroding ever since the Laramide orogeny that resulted in uplift of the Wind River Mountains some 70 million years ago. In other words, erosion of the lodes at South Pass has been supplying gold to these placers for tens of millions of years! Based on geology, the two better placers are Rock Creek and Willow Creek.

Rock Creek Placer
The South Pass greenstone belt encloses many in-situ lode and detrital placer deposits. As the lode deposits erode, they supply gold to drainages (placer deposits). Near the head of Rock Creek, Willow Creek, Smith Gulch and Atlantic Gulch is a prominent belt of gold-bearing shear zones (lodes) that is the source of much detrital gold found in the placers. It is also likely there are hidden lodes in this region, which the author found evidence for while mapping. Even so, the closer the placers lie to the known belt of shear zones, the greater the likelihood coarse gold (nuggets) will be found in stream gravel. Fine gold will likely occur throughout much of the Rock Creek placer from Atlantic City to the Sweetwater River. The headwaters of Rock Creek lie near the abandoned Atlantic City iron ore open pit mine and the town of Atlantic City sits immediately downstream and sitting on many known gold-bearing shear zones including the projected trend of the Carissa lode (Figure 4).

Portions of Rock Creek were mined from 1933 to 1941. Pre-1933 gold placer mining operations on Rock Creek were likely localized hydraulic operations designed to wash gold from slopes of adjacent hill sides. Some early hydraulic mining on Mill Hill along the south edge of Atlantic City (south bank of Rock Creek) was reported to have produced 10,500 ounces of gold. Without the use of dredging, trommel plants, pumps, or hydraulic mining, placer operations within Rock Creek would have been limited and largely ineffective due to the stream’s gradual gradient (2°) that is not favorable for gold recovery by sluice. A sluice  would require a higher water velocity for gold concentration than that supplied by such a gradual steam gradient.
Figure 4. Generalized geological map of the Atlantic City-Miners Delight-
South Pass district (after Bayley, 1968; Hausel, 1989) showing location of
principal gold mines. Mine locations and dikes  (horizontal lined
 patterns) mark locations of many gold-bearing
shear zones. Since these are the source of much
of the gold in the district, any placer
downslope from these will have gold and the size of nuggets
should decrease downstream
 from the shear zones. It should be kept in mind that there are
likely hidden shear
zones downstream (east) from principal lodes.

   
Historical reports indicate that rich gold specimens were found in Rock Creek. For instance, one fist-size piece of gold was reported to weigh 34 ounces and a boulder found nearby in 1905 contained an estimated 630 ounces of gold (Figure 5)! 
A 34-ounce gold nugget recovered from Rock Creek, Wyoming. Photo
courtesy of the Los Angeles Natural History Museum.

The Rock Creek channel is 100- to 250-feet-wide and locally narrows to tens of feet wide. At narrows, water velocities will decrease providing one of several types of placer gold traps in Rock Creek. For example, Rock Creek narrows immediately downstream from Atlantic City at the following GPS coordinates (see: Google Earth 42°29'34"N; 108°43’21”W). Another favorable trap likely occurs at stream meanders where water velocity again decreases (see 42°27'38"; 108°40’W).  


Figure 5. A 7.5-ounce nugget found with metal detector,  

Other traps likely occur in Rock Creek, such as at fault zone intersections with the creek (see: 42°27’44"N; 108°40’2”W). Examination of aerial photography on Google Earth shows a distinctly linear drainage on the west bank of Rock Creek that likely is controlled by an underlying fault. Other traps will occur where tributaries intersect Rock Creek, such as at Smith Gulch (42°28'26"N; 108°40’51”W).

Between 1933 and 1941, the E.T. Fisher Company constructed a concentrating plant with trommel and mined with an unattached dragline in order to dredge 6 miles of Rock Creek from Atlantic City to the Mormon Cemetery. Approximately 3 million yds3 of gravel were processed that averaged 0.012 oz/yd3. Production was reported as 11,500 ounces. However, based on the volume of gravel and average ore grade, production should have been 3 times higher than the reported production (about 36,000 ounces); thus, it is possible the operation lost considerable gold to the tailings. Nuggets up to 3.4 ounces were recovered in the first year of operation. 

Figure 6. Rock foliation in metagraywacke (dark-gray, micaceous quartzite) of the Miners Delight Formation along Rock Creek. The foliation is nearly perpendicular to the flow of Rock Creek and stands nearly vertical (at an acute angle). Rock Creek cuts 12 to 14 miles of rock foliation of the Miners Delight Formation before draining into the Sweetwater River. The foliation provides thousands of ridges and grooves that act as natural riffles at the base of Rock Creek similar to manufactured riffles in a sluice or Wilfley Table. These natural riffles likely captured considerable gold in the stream bottom.
The average soil depth for Rock Creek was reported as 10 feet and ranged from 9 to 12 feet deep. The upper 3 feet consisted mostly of loam (sand, clay and gravel) which was thought to be barren of gold and was rejected by the Fisher Dredge. Gold prices during the E.T. Fisher mining operation from 1933 to 1941 were 35 to 45 times lower than today ($26.33 to $34.87/ounce compared to $1,140/ounce on 9/3/15). Even so, the loam piles contained fine gold that was not extracted by the mining operation (Figure 7).

Much of the gold recovered from the creek in the first year of operation of the dredge, was found within 1 to 3 feet of bedrock, with the greatest concentration found within the 6 inches above bedrock. The gold was reported to occur as flakes, small particles and uncommon rounded nuggets with a typical fineness of 0.840 to 0.900 (84 to 90% pure gold). 

Figure 7. Gravel and loam piles from the Fisher operation on Rock Creek.  In addition to unmined tributaries, Rock Creek also has 3 miles of unmined gravel downstream from the Mormon cemetery. Unmined gravel also lies upstream from Atlantic City as well as throughout the mined portions of the drainage. Essentially, all of the loam piles remain untested for gold content and provide a potentially large resource if the fine  gold can be efficiently recovered. The mined gravel piles also contain some rejected gold. Even though these were mined and processed for gold, the processing plant did not appear to be efficient since gold can still be found in the tailings. For instance, one prospector from the RMPTH club in Ft. Collins showed me a collection of more than 100 nuggets recovered from gravel piles along Big Atlantic Gulch and Rock Creek using a metal detector. 

Figure 8. False bedrock provides another of many gold traps in Rock Creek.
At least one false bedrock layer was found in Rock Creek and in Smith Gulch.
The layer lies above bedrock providing a nearly impermeable barrier to gold.
This impermeable layer provides a trap for gold in the gravel
immediately above the layer. 
During a 1987 mining operation on Smith Gulch (a tributary of Rock Creek), prospectors Hank Hudspeth and Buddy Presgrove recovered about 20 ounces of gold per week, and periodically hit pay streaks yielding 20 ounces in a day. The gravels were 6 to 10 feet deep, and gold occurred as flatten nuggets and flakes near bedrock and in the sandy and gravel layers overlying thin clay-rich, false bedrock, zones. The gravel averaged about 0.1 ounce/yd3 (Hausel, 1989, 1991). These layers likely formed during periods of drought, that were followed by flash flooding (photo by W. Dan Hausel).


Prior to 1911, 750 ounces of gold were mined from Atlantic Gulch. Big Atlantic Gulch was later dredged by the Fisher dragline. Near the mouth of the gulch, the stream narrows considerably. The upper reaches of Big Atlantic Gulch from the Snowbird mine north to Cole and Placerita gulches, contains some unmined gravel.

Little Atlantic Gulch, a tributary of Big Atlantic gulch, lies west and parallel to Big Atlantic Gulch and cuts the same rock and shear zones. There has been very limited activity in this gulch. Further west, are a group of small gulches that are dry much of the year. These include Basket Gulch, Beer Garden Gulch, and others. East and parallel to Big Atlantic Gulch, are Smith and Promise gulches. Prior to 1911, 1,500 ounces were recovered from Smith Gulch and about 1,500 from Promise Gulch, yet some gravel remains unmined in these drainages.

E.T. Fisher Plant & Dragline

Figure 9. The E.T. Fisher gold processing plant, Rock Creek
 in 1934. Photo from the Edna 
Carpenter collection.
In 1935, Ross and Gardner from the US Bureau of Mines examined the E.T. Fisher  placer mining operation. At the time, the dredge had only been in operation a very a short time, thus we know practically nothing about the operation after 1934 until the outbreak of World War II when all gold mining operations were ordered closed by the government.. 

According to their report, the riffles used to extract gold from the plant were charged with about 100 pounds of quicksilver (mercury). It was reported 30% of the mercury was lost during sluicing and cleanup. This would imply that in one of the most important processes used to extract gold from this plant was only about 70% efficient. 
Figure 10. Remains of the E.T. Fisher processing plant on Rock Creek as it
appeared in 2015 (photo by W. Dan Hausel)
.
Mercury is a very heavy metal with a specific gravity of 13.6 (gold is 19.3) that was used to amalgamate with gold. Such a high mercury and amalgam loss indicates there was a problem with water velocity from the pumps in the recovery plant and/or the angle of the sluice was not at an optimal angle.

Ross and Gardner (1935) indicated that the dragline dug to the bottom of the creek. Their report indicates 18 inches to 2 feet of bedrock was typically scraped and processed with the gravel.  

Summary
Based on the successful nugget recovery in the Fisher gravel piles by various prospectors using metal detectors, there was a generally poor nugget recovery efficiency of the Fisher operation. In addition, the loss of 30% of the gold-mercury amalgam suggests other inefficiencies in the Fisher operation, and the avoidance of fine gold by the miners provides more evidence of the gold left behind by the mining operation. In 1987, the author visited the Gerald Stout mining operation located in a small piece of virgin ground in Rock Creek: this operation recovered considerable gold and it appears there could be considerable, unmined, virgin ground in Rock Creek. For instance,  the Fisher operation piled gravel and loam on the ore body while mining other parts of the creek; thus there could be considerable virgin ground in Rock  Creek (Figure 12). Whether there is enough gold for a commercial operation remains unknown. 

Figure 11. Rock Creek mine tailings provide not only sites for finding gold
lost during the initial mining operation in the 1930s, but also for
a giant resource for gravel (photo by W. Dan Hausel).
In addition to gold, there are other value-added materials including considerable gravel (Figure 11), decorative stone and sand. 

Other value-added commodities that should be investigated include: (1) frac sands, (2) gemstones, and (3) tungsten. After sieving any loam piles, any recovered sands should be examined for potential use as a frac sand for use in the oil industry as there should be considerable sand recovered by mining loam piles for gold. 
During gold mining, tailings should periodically be examined for gemstones. The metamorphic grade in the South Pass region is favorable for a variety of aluminuous gems including garnet, andalusite, sillimanite, cordierite, ruby and sapphire. In the past, there was one report of a gem-quality diamond found at South Pass and the author has also identified nearby unexplored cryptovolcanic structures. In the Louis Lake area northwest of South Pass, some high-quality gem aquamarine was recovered, and some could potentially end up in the South Pass placers. As a final note, scheelite (tungsten ore) was identified in the Lewiston gold district along the eastern margin of the greenstone belt. It is unknown if scheelite occurs in Rock Creek, but because scheelite (calcium-tungstate) is a heavy mineral, it can be recovered in a gold sluice. Rock Creek looks to be an excellent gold prospect.

I would like to thank  by James Healey and RC Mineral and Rock, LLC  for contracting me to examine their Rock Creek gold property.
Frozen in time. The E.T. Fisher gold dredging operation on Rock Creek, Wyoming, commercially produced gold
from Rock Creek at $32.32/ounce to $35.50/ounce. The operation ceased in 1942 when closed by
 War Minerals 

Board Order L-208 that was designed to focus the US mining industry on mining and recovery of metals needed for
World War 2. This mine, like many in the US, never reopened (Hausel, 2019). With gold prices of today (9/22/2019) as
high as $1500/ounce (more than 40 times its value when the mine closed) (see gold prices at Gold Prospector), Rock Creek
 should be considered a viable gold target. All of the ground from the processing plant, continuing downstream to the 
Sweetwater River is virgin ground and very likely has commercial gold at $1500/ounce. The same hold true for Willow
Creek and many tributaries in the district. Note the placement of gravel and loam piles sitting on unmined ground.
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  • Pfaff, B.C., 1978, Atlantic City nuggets with stories and history of the Atlantic City-South Pass area: Bariol, Wyoming, 155 p..
  • Pfaff, B.C., 1997, Fine Gold. Broadway Books.
  • Ross, C.L., and Gardner, E.D., 1935, Placer methods of the E.T. Fisher Company, Atlantic City, Wyoming: US Bureau of Mines Information Circular 8809, 31 p.
  • Snyder, G.L., Hausel, W.D., Klein, T.L., Houston, R.S., and Graff, P.J., 1989, Precambrian Rocks & Mineralization, Wyoming Province: 28th International Geological Congress guide to field trip T-332, July 19-25, 48 p.
Steve Gyorvary at Atlantic City, Wyoming. An outstanding miner and
geologist
The highlight of my consulting trip to South Pass was
seeing my old friends - Steve Gyorvary and
Gerald Stout. I thank God for these times in my life. 
Old Friends meet again. This group photo shows members of my last public field trip many dozens throughout the years,
The photo shows the GemHunter to the far left of the photo in Khaki shirt and with hat. Standing behind me is my son,
Eric.Also in the photo, is my good friend - Steve Gyorvay. Steve in kneeling in the center of the photo. 


Monday, December 17, 2018

South Pass gold district - prospecting from the air.

Dan Hausel (GemHunter) stands in front of the 
Atlantic City Hilton at South Pass.

I was paid by the Wyoming Geological Survey at the University of Wyoming, along with some federal US Geological Survey grants to live in a tent for 5 summers in the 1980s and map and explore the South Pass greenstone belt. The state supplied me with nourishing instant oatmeal, spam and instant coffee for breakfast, lunch and dinner, while I lived in my personal tent and mapped the 250-square-mile greenstone belt and its gold and iron ore deposits, mines and mineralized trends. Some weekends, I splurged and wandered into the Atlantic City Mercantile to buy a beer and talk to locals to gain insight into their prospects.

Start with a web search on ‘South Pass gold’, then expand the search to ‘South Pass gold prospecting’. Already, you should be finding information on gold deposits, geology, mines, mining districts and towns. Now expand to ‘South Pass gold mines’. As you find mine names, search the web for those mines. It doesn’t take long and you will have a considerable file.

Now examine South Pass on Google Earth. Search “Atlantic City, Wyoming 82520”. This will take you to one of the larger cities in the state at the base of the Wind River Mountains. When I was a ‘snowbird’ resident of Atlantic City living in a tent, the city population sign read “population about 57”. This was probably an exaggeration unless you include pets.

Examine the region at an eye altitude of 50,000 to 10,000 feet on Google Earth and you will see prominent rock lineation that trends roughly E-W to E-NE in hills surrounding Atlantic City. Move your stylus to 42°29’10"N; 108°40’18"W just east of Atlantic City for an excellent aerial view of lineation. The lineation is prominently expressed in the Miners Delight Formation, a thick rock unit formed mostly of meta-graywacke. ‘Meta’ refers to the fact that the graywacke is metamorphosed (recrystallized), and ‘graywacke’ refers to a ‘dirty’ sandstone that has considerable sand, clay and silt that later recrystallized to a mica-cordierite-andalusite quartzite (metagraywacke).

These rocks were abused by tectonic deformation and squeezed into a steeply-dipping and plunging basin 2.8 billion years old such that we now see the edges of the meta-sedimentary (and meta-volcanic) layers. To visualize this, take a book and lay it flat on a table in front of you. Imagine the pages represent layers of rock deposited on top of one another. Now rotate the book 90 degrees and sit it on the binder. As you view each page on end, they will appear similar to lineaments at South Pass, so now you should have some idea of what happened at South Pass. All of that lineation you are looking at on Google Earth is the metamorphosed sedimentary and volcanic rock beds that have been tilted 90 degrees (more or less) and now sitting on end. Try to imagine the force required to do this to this part of the earth’s crust. To make things more complicated, the entire belt was also folded like an accordion and recrystallized.

As you admire some drainages at South Pass on Google Earth such as Big Atlantic Gulch, Rock Creek, Meadow Creek and portions of the Sweetwater River, keep in mind that hundreds of nuggets came from these drainages in the 19th century, and are still being found to this day. Big Atlantic Gulch, Rock Creek and Meadow Creek cut rock foliation, which is good to keep in mind when prospecting for gold placers. Since gold-bearing structures in this region lie parallel to nearly parallel to foliation; thus, any drainage that cuts foliation will sample these gold-bearing structures and the foliation will provide natural riffles at bedrock.

When I mapped South Pass, I came across two prospectors (Buddy Presgrove and Hank Hudspeth) exploring for gold in Smith Gulch (42°31'3"N; 108°42’19"W) with backhoe and trommel. They recovered gold from two pay streaks: one on bed rock, and the other on false bedrock about 4 feet above bedrock. The two recovered about 20 ounces of gold per week in an area that arm chair prospectors claimed had no gold or was all ready mined out.

There are many placers and lodes of potential interest in this area, as there are in most gold districts. Placers that continue to yield nuggets include Rock Creek (42°29'11"N; 108°42’25”W), Spring Gulch (42°31'59"N; 108°40’43"W), Big Atlantic Gulch (42°29'54"N; 108°42’31”W), Meadow Gulch (42°27’49"N; 108°47’9"W) and parts of the Sweetwater River. To obtain information on ownership visit the Fremont County courthouse in Lander and the State BLM office in Cheyenne.

Monday, July 24, 2017

Ode to South Pass

Twas the spring of ’78,
When prospectors tipped beer with squirrelly mates, 
At the Mercantile we heard cheers and moans,
Interrupting exaggerations about gold in shear zones.

Along came a geologist named GemHunter Dan,
Twas said to be a hard rock man, 
Surrounded himself with rocks of old,
Including amphibolite, a host for gold.

The GemHunter
In the summer, when snow buried his tent, 
Off to Laramie is where he went,
He swore he would be back with hammer and map,
And would also bring a miner’s cap.

Atlantic City with population of 40,
Dogs, Barbara, Steve, Tony and Shorty,
Blessed by a geologist with all his maps,
Found gold at a mine face covered with bats.

Down the shaft in stopes so cold,
Then up in a raise he was told,
Is where the yellow metal resides so bright,
In tunnels and chutes lit by a miner’s light.

The Carissa kept its secrets deep,
Until the State took her while we weeped,
A billion in gold, now lay with mold, 
So tourists can enjoy a town of old.

There was a Mary Ellen mine and its mill,
With Steve the captain at the wheel,
We descended 240 feet of incline, 
Followed the vein while my assistant whined.

He’s claustrophobic at 240 deep,
Carrying him up a ladder that’s way too steep,
So we yelled “Jay” climb to the light,
He made the head-frame before midnight.

Then there was Barbara so bold and old,
Swindled a tourist with jars of fool’s gold, 
The pyrite was shiny, brassy and cold,
But the tourist was mad when he was told.

He plugged his whiskey bottle with a cork,
Decided to get even by calling her dork,
And that evening, while she slept on a floor,
Barbara’s Cadillac was ablaze from door to door.

Gold panned out of the Rock Creek dredge tailings
Barbara awoke to whisky and flakes,
We wondered who next she would take,
When into the Mercantile strolled a mark,
Dressed like a dandy at the bar he parked.

Where’s the Mary Ellen he asked so kind,
So Barbara offered him title to a mine,
No thanks said the gentleman from Missouri,
You see, I’m really in a big hurry. 

Besides the mine cannot be sold,
After all its my mine he told,
So Barbara drank another shot,
Another swindle and she was caught.

Then there was Shorty with wet pockets and old, 
Sat in his trailer to count his gold,
Cut a hole in a single wide on Rock Creek, 
To fill his honey pot and make everyone reek.

Atlantic City is the place,
To mine gold and investors with hast, 
Dig the gravel and fill a mucker,
A sluice, a pan, or a sucker.

Enough! I said as I headed out with cap,
Grabbed my Brunton and began to map,
Eight quadrangles, 500 square miles, a dozen or so mines completed,
Searched for the yellow stuff and found more Mormons than needed.

Published a paper a book and cried,
Why do bureaucrats have to lie,
Elected a crooked Democrat, 
With a State geologist, a two-bit rat.

So long I said to South Pass of old,
You can keep your Democrat and your gold,
Wyoming democrats smell ripe and old,
Just like Shorty’s honey pot I’ve been told.


Mining districts and mineralized terrains of Wyoming 
(after Hausel, 1997; and Hausel & Hausel, 2011). 
South Pass, what a glorious place! I saw South Pass for my first time in 1978. The vast gold mining region and greenstone belt along Highway 28 at the southern tip of the Wind River Mountains was just south of the town of Lander in western Wyoming. It was love at first site! The geology, the old mines, a couple of tiny towns partially occupied by ghosts - it was a geologist’s paradise. 

I told the greenstone belt, "I will be back to map you". And, I did get back and accumulated fond memories during the five summers in a tent while mapping the 450 to 500-square mile granite-greenstone belt and more than two dozen gold mines.

South Pass is a gold prospector's paradise. At least it use to be. The geology forms a tightly folded, granite-greenstone belt, a geological basin, with banded iron ore deposits along the western and eastern limbs of the belt. If you are unfamiliar with this kind of geology, I recommend searching the Internet for a summary on ‘greenstone belts’. Archean age ‘greenstone belts’ and ‘gold belts’ are often synonymous terms to geologists who work in Archean (older than 2.5 billion years) rocks.

Schematic map of the South Pass granite-greenstone belt 
showing location of the South Pass-Atlantic City and Lewiston 
districts, and McGraw Flats and Oregon Gulch paleoplacers (after Hausel, 1991)
Decades ago, iron ore was mined at US Steel’s Atlantic City mine; a mine that was a show-case for the company. But, the once majestic mine closed and is now a lake (42°32'26"N; 108°44'44"W) sitting along Highway 28.

The iron ore occurs in a rock known as banded iron formation (BIF), or taconite. It consists of alternating layers of magnetite and quartz. BIF is a good source for iron, and some are also sources for gold, particularly where quartz veins and sulfides such as pyrite, chalcopyrite or arsenopyrite occur in the rock. Take the Homestake mine as an example: nearly 40 million ounces of gold were mined at Homestake over a century, and it was classified as iron formation. Other examples of gold in iron formation occur at the Lupin mine in the Northwest Territories, Detour Lake in Ontario, Mt. Morgans in Western Australia, and others in Zimbabwe, India and Brazil.

Folded BIF from the Atlantic City iron ore mine, Wyoming, with
quartz veinlets, 
The BIF at South Pass lies in a meta-sedimentary unit known as the Goldman Meadows Formation that includes mica schist and quartzite resting on older rock of the Diamond Springs Formation. The average iron content of the BIF is upwards to 40%. US Steel operated the mine and recovered more than 90 million tons of iron ore prior to closing the mine in 1983. The geology of the Goldman Meadows formation indicates these rocks were originally deposited in a shallow sea on a stable platform possibly 3 billion years ago.

Copper-stained BIF from the Seminoe Mountains greenstone belt,
Wyoming, with both black and white quartz veinlets
mixed with dark gray magnetite.
When the Atlantic City mine closed, the BIF was unsampled for gold until I asked about archived gold assays. The company was so focused on iron, they didn’t consider the possibility of gold. I got permission to visit the mine, but my annual assay budget at the Wyoming Geological Survey was a pitiful $100 per year (at that time, $100 would cover 3 to 5 assays), so I was unable to test the rock for gold since I had already spent my annual assay budget. Even so, I found quartz veinlets cutting the BIF with pyrite and chalcopyrite as well as other veinlets that penetrated the rock foliation - good signs for gold. Even so, I was unable to prove the rock had any gold. But when the beer started flowing at the Atlantic City Mercantile and I brought up the subject, former iron miners swore they had seen visible gold in the open pit. In 1981, I had found highly anomalous and localized gold in BIF in the Seminoe Mountains greenstone belt east of South Pass, but we still don't know if there is any gold in the BIF at South Pass. 

The Diamond Springs Formation, the lowermost mappable rock unit at South Pass includes primitive, metamorphosed, igneous rock known as amphibolite (metamorphosed basalt) and serpentinite (metamorphosed komatiite). Samples of this material contain 18 to 38% MgO, a trace to 1.0% chromium; and trace to 0.26% nickel. Based on chemistry and rock mineralogy, I interpreted these ancient and altered rocks to originally be basalts and komatiites deposited on the earth’s surface 3 billion years ago. Komatiites are rare volcanic rocks often found in greenstone belts and are essentially restricted to Archean age (older than 2.5 billion years).

Locally, some of the serpentinites have cross-fiber asbestos veinlets that were prospected in the early 20th century for asbestos, while other outcrops are massive, and a few have cumulate texture. Cumulates are magnesium-rich metamorphosed volcanic flows that erupted directly from the earth’s mantle and when they began to cool, tiny olivine grains crystallized in the lava, sank, and accumulated at the bottom of the flow producing a sandstone-like, cumulate texture. 

Rock foliation and bedding of dark gray to black meta-greywacke 
of the Miners Delight Formation is nearly perpendicular to Rock 
Creek with its dredge tailings in the foreground. In other words, the 
bottom of rock creek is lined with many natural riffles to trap gold. 
By the way, the name ‘Miners Delight’ would be better applied to a beer.

Magnesium-rich volcanics are good rocks to prospect for nickel, chromium, platinum-group metals and gold: none of which I detected in anonymous amounts at South Pass. Elsewhere in Wyoming, I found anomalous nickel and palladium in another magnesium-rich rock at Puzzler Hill in the Sierra Madre Mountains, and chromite was found nearly a century ago in serpentinite in the Laramie Mountains near Douglas. Nickel anomalies are also reported in the Laramie Mountains anorthosite complex, where a king’s ransom in labradorite (spectrolite) and iolite gemstones occur. 

As a rock hound or prospector, any time you see the term 'anorthosite', it usually means it's a good place to search for labradorite. And if you are interested in iolite - that is a little more complicated. Look in areas where the rocks have been metamorphosed and have high alumina. Or, simply look for the term 'cordierite' applied to metamorphic rocks. Cordierite is the geologist's designation, and few geologists know what gemstones look like. Often they mention the mineralogical term but completely overlook the fact that the mineral may be gem quality. But remember, there is a lot of cordierite out there that is very poor quality.

At one location north of Laramie based on the few samples I collected on a county road, and based on historical estimates of the amount of cordierite exposed in trenches, there could be a deposit with more than a trillion carats of iolite. Nearby, I found some extraordinary deposits of iolite at Palmer Canyon and Grizzly Creek. Iolite is a low-value gem.

Miners Delight mine was developed on a 3 to 16 foot wide shear zone that has been traced over 2500 feet on the surface. Gravels in nearby Spring Gulch draining this shear zone produced 1500 ounces of gold including several 1 & 2 ounce nuggets, a 6 ounce nugget, and a sample of auriferous quartz described as “the size of a water bucket that was filled with gold”. Samples collected across the shear zone by the the author assayed from 0.01 to 0.36 ounce per ton gold.  A historic prospectus reported there were 2,400 feet of drifts accessed from a 250 foot deep shaft and the mine produced 60,000 ounces. The gold tenor ranged from 0.3 to 110 ounces per ton of gold. It is likely that this property still has considerable ore at depth.
Some gemstones are also found in serpentinites - for instance, my good friend Robert Odell (RIP) found hundreds of tiny, blue sapphires in alumina-rich serpentinite near the Red Dwarf ruby deposit in the Granite Mountains of central Wyoming northwest of Jeffrey City. While exploring northern California for diamonds, I came across chromian diopside in serpentinite. Chromian diopside is considered to be a kimberlitic (diamond) indicator mineral and some specimens yield spectacular emerald-green gems. In central California, east of Sacramento, I also found gem-quality benitoite in the river adjacent to a serpentinized breccia pipe I examined for diamonds. The benitoite was flawless and likely eroded from nearby aluminum-rich serpentinite. I was hoping to get back to that area some day and search for the source for those gemstones, but never did. Even though some serpentinites contain gemstones, the South Pass serpentinites lack anything of value, other than for a few crooked jade dealers who sell it as jade.

The base of the South Pass greenstone belt is interleaved with gneiss. Similar gneiss found elsewhere in the Wind River Mountains is dated from 2.8 to as much as 3.8 billion years old. Age dates in the South Pass granite-greenstone belt include the Louis Lake granitic batholith (which intrudes the greenstone belt) and is dated at 2.6 billion years old. Some poor quality helidor (yellow-green beryl) and rare aquamarine beryl occurs in granite pegmatite associated with this batholith. A 2.8 billion year age (isochron) was determined for the Miners Delight Formation metamorphic event that recrystallized all of the rocks of the greenstone belt. A similar age was determined for a vein at the Snowbird mine located in the Miners Delight Formation, suggesting that a temporal connection exists between metamorphism (rock recrystallization) and gold mineralization. It is likely much of the primary gold at South Pass leached out of the rock during metamorphism and migrated to zones of lower pressure (i.e., fractures), such as shear zones that lie parallel to near-parallel to regional rock foliation. Thus, when prospecting at South Pass, it is important to learn as much as possible about these shear zones.

False bedrock on Rock Creek (42°29'10"N; 108°42'22"W). Layers of false 
bedrock can lead placer miners to give up after they recover gold from a 
pay-streak thinking they are on bedrock. The handle of the shovel rests 
against the massive clay layer (claystone) that acts as a barrier to gold. 
Siting above this layer, cobbles and pebbles in the overlying conglomerate 
are characteristic of stream gravel and this material carries gold which 
is enriched at the interface between the conglomerate and the claystone. 
Below the claystone, more gold-bearing steam gravel is visible. As one 
digs further down into the placer on Rock Creek, similar false bed rock 
layers will likely be found. On Smith Gulch (42°31'3"N; 108°42'19"W), 
two placer miners (Hank Hudspeth and Buddy Presgrove) found a similar 
false bedrock layer with considerable gold sitting on false bedrock and  
found additional gold below the layer on actual bedrock. 

Sitting on the Goldman Meadows Formation is the Roundtop Mountain Greenstone Formation - a belt of metamorphosed pillow basalts deposited in an ancient sea. Some pillow basalts are so well preserved that I was able to use them the tell which way was up in this part of the stratigraphic section. This is helpful when mapping rocks in greenstone belts, because most greenstone belts were compressed and squeezed like an accordion during tectonic stress, and many rock units can be overturned. 

If you are not familiar with pillow basalt but familiar with the Black Cat snake fireworks made from sodium bicarbonate and sugar, you have a good idea of what pillow basalts look like. Pillow basalts erupt under water expanding like snakes. Where they rest on a rock layer, they tend to sag until they completely solidify and look like a pillow. Since they sag, one can determine which way was up at the time of deposition. The pillow basalts at South Pass are now tilted nearly 90o.

The Roundtop Mountain Greenstone is overlain by the Miners Delight Formation, which is estimated to be 5,000 to 20,000 feet thick and seen throughout much of the exposed greenstone belt. Determination of the thickness of this unit is complicated by folding and faulting, and in most places it has been tilted nearly 90o and many places it is overturned. This formation consists primarily of dark gray to brownish black meta-greywacke. Greywacke (or meta-greywacke) is nothing more than dirty sandstone deposited along the edge of an ancient continent.

Non-mineralized rocks of the Miners Delight Formation contain a trace to 0.051 ppm Au (gold) (compared to a worldwide average of 0.002 ppm. Essentially all of the rock units at South Pass exhibit above average gold content and these were deposited in a shallow to moderately deep oceanic basin by volcanic activity and erosion of an adjacent continental shelf. All of the old Archean rocks were intruded by a belt of gabbroic rocks along a rift. These intrusive rocks are now classified as amphibolite but were originally gabbro, diabase, andesite and komatiite. 

As the entire belt was compressed and folded along the edge of the subduction zone 2.8 billion years ago, shear zones formed along the contact between the Miners Delight meta-greywacke and the amphibolites due to the competency contrast between the two rock types. This is a very important concept for gold prospectors. Wherever you find shear zones at South Pass, you usually find quartz stringers, quartz lenses, fractures, limited hydrothermal rock alteration and gold! So, take a look at Google Earth and scan from South Pass City (42°28'7"N; 108°48'10"W), to Atlantic City (42°29'46"N; 108°43'49"W), to the Miners Delight ghost town (42°31'60"N; 108°40'51"W) and place pins (placemarks) on mines, trenches and prospect pits. Not only will your fingers wear out placing pins in prospect pits, but soon you will visualize the trend of the shear zones. They form a northeasterly belt running along the western limb of the greenstone belt. If you do the same for the Lewiston district 11 miles to the east, you will see a similar pattern emerge.

The Duncan mine and mill, 1989
Parts of the South Pass greenstone belt are overlain by geologically young sedimentary rocks of Tertiary age (65 to 2.6 million years old) that include gold-bearing conglomerates in the Wasatch, White River, Arikaree, and South Pass Formations. When you prospect at South Pass, you will periodically see lenses of younger rocks scattered high and dry away from any known drainages - if they look like they have pebbles, cobbles, and boulders, dry pan them for gold. On past gold prospecting and geology field trips, I often stopped at one or two of these sites (42°28'45"N; 108°42’58"W) so prospectors could see another type of gold deposit found in the greenstone belt that has been overlooked. 

The more I mapped South Pass, the more it was clear that only a portion of the greenstone belt was visible at the surface and large parts of the complex continued under younger sedimentary rocks to the north and south. Geophysical exploration and drilling by Hecla Mining Company discovered greenstone belt rocks under a thick layer of sedimentary rocks, 6 miles south of South Pass City. Hecla had an excellent gold target at that location that their geologist (Foster Howland) interpreted as a buried, sulfide-rich iron formation, but the drilling project was cut short due to a recession.

The Carissa mine was developed in an intensely folded and faulted structure known as a shear zone. The primary high-grade gold-
bearing shear structure is 1.5 to 80 feet wide. This high-grade zone is enclosed by a much larger, completely unmined, low-grade shear envelope that is as much as 1000 feet wide! The envelope is almost completely untested even though samples show potential for a major gold deposit! A 97-foot composite chip sample that I collected on the south side of the high-grade shear within this low-grade zone yielded 0.023 ounces per ton. Another 30-foot sample on the north side of the high-grade shear yielded 0.07 ounces per ton of gold! The remainder of the envelope (about 850 to 900 feet) remains untested!.

The Carissa ore deposit is structurally controlled and appears to represent a saddle reef deposit where high-grade gold is localized in fold closures and rehealed fractures similar to the Homestake mine. Geological evidence suggests the Carissa orebody continues to great depth. Support for the presence of a major ore deposit includes drilling that tested the mineralized shear below the mine workings. Drilling by Consolidated McKinney Resources identified a highly anomalous zone that was up to 80 feet wide. Assays of drill core from this zone ranged from 0.03 to 2.54 ounces per ton gold (the shear envelop was not tested). This mineralized structure was intersected at depths up to 930 feet. In addition, Carissa Gold Inc. made the following reserve estimates on the property using a very high reserve cutoff grade. They reported the mine had 208,000 tons of ore with an average grade of 0.343 ounces per ton and a geological reserve of 37,000 tons of ore averaging 0.85 ounces per ton!

Anaconda Minerals also drilled the property and all of their reported drill holes interested ore grade material. They intersected a high grade ore zone over widths of 2.3 to 16.1 feet that yielded 0.11 to 0.36 ounces per ton gold at depths up to 700 feet. Again, they also ignored the shear envelop, which likely contains considerable gold that is minable at today’s gold prices.
In this region near Oregon Buttes (42°15'19"N; 108°51'21"W) and Dickie Springs (42°18'30"N; 108°51'48"W), Wasatch Formation conglomerates are estimated to be 1,300 feet thick and cover 8 mi2. Some gold-bearing oil well cuttings were recovered from depths of 6,500 to 7,000 feet just north of the Continental Fault to the north of Oregon Buttes. This vast gold-bearing paleoplacer has been mostly ignored for decades, except at the Dave Freeman prospect, where Dave has been recovering gold from the dry placer. 

Erosion over millions of years left behind extensive Eocene paleoplacers along the north and south ends of the greenstone belt. One estimate by the US Geological Survey suggested the paleoplacers south at Dickie Springs and Oregon Gulch could contain 28.5 million ounces of gold! But the gold is distributed throughout a very large volume of conglomerate, and little to no standing water is available except at Dickie Springs. So, one either brings water to the conglomerate or vise versa. But just like any placer, these paleoplacers have pay streaks associated with black sands that contain magnetite, so a search using magnetic surveys may assist in identifying pay streaks.

Remains of the E.T. Fisher washing plant on Rock Creek. This mine operated from the 1933 to 1941. How good are your eyes?
 Can you see the beginning of World War 2 in this photo? It's pretty obvious. When WW2 broke out, all non-essential mines were
 ordered closed by the War Miners board - which included all gold mines. This placer operation on Rock Creek was still recovering
 commercial amounts of gold, when it was ordered to close. The mine (like many gold mines at that time) never reopened. Gold
 prices were $35.5 per ounce in 1941 as compared to $1,250 per ounce today. Few people have ever tried to reopen these old
 placer and lode gold mines that were ordered to close, even though they are almost guaranteed to be commercial. 
Learn as much as you can about shear zones: this is where the primary gold will be found. And, all of the good placer gold deposits are found a short distance downstream from shear zones. As you dig for placer gold in the drainages, keep in mind you will likely find pay streaks on false bed rock surfaces, with additional pay streaks on bedrock.

There are undoubtedly pay streaks downstream from many shear zones in the South Pass-Atlantic City-Miners Delight district and in the Lewiston district to the east. If I were to look for nuggets, I would examine places like Hermit Gulch (42°28'29"N; 108°47'23"W) since it is down slope from many good gold-bearing shear zones near the Carissa mine. Then there is Little Beaver Creek (42°29'26"N; 108°45'5"W) downstream from the Duncan, Mary Ellen and other mines. Spring Gulch lies downstream from the Miners Delight mine (42°31'55"N; 108°40’57”W) where many nuggets were found in the past and in the Lewiston district, there are several, small, immature, dry drainages downstream from shear zones. Most do not have much dirt, but that dirt likely has some gold. Some of these lie near a couple of shear zones that host the Goodhope (42°26'32"N; 108°32'22"W), Mint (42°26'32"N; 108°32’45”W), Gold Leaf and other mines that produced some excellent gold specimens in the 1980s and likely in the 1800s and early 1900s. The more you look around these shear zones, the more targets you will spot.

In the past, some of the better placer gold was collected on Rock Creek (I’ve seen over a hundred nuggets from the area) and Big Atlantic Gulch, and the better gold-bearing rock samples were collected at the Carissa mine (42°28'29"N; 108°47'42"W). So common was visible gold at the Carissa mine, that every field trip I led to the area, at least one person found a very attractive gold specimen on the mine dump. And I’m sure there were many I never heard about.

Hematite-stained quartz breccia with considerable visible gold in vugs
found at the Carissa mine. This became a common occurrence over
the years. Essentially every field trip the author led to South Pass
someone found specimens with visible gold. Most were found at
the Carissa mine. Other localities where visible gold in quartz was
 found included the Duncan, Miners Delight, Mary Ellen,
Good Hope, Mint and others
Based on assay samples taken at the Carissa mine (42°28'29"N; 108°47'42"W) by past mining companies and myself, a significant gold deposit continues along the Carissa-Duncan-Mary Ellen trend and down-dip for at least a thousand feet. At the Carissa, the mineralized shear zone is as much as a thousand feet wide. Past miners focused only on the high-grade gold in the narrow, prominent, shear structure, and completely ignored a very large envelope of low-grade gold. Past drilling showed the gold-bearing structure was mineralized to depths of 930 feet. This was the deepest any drill hole penetrated the gold structure - so, it could easily continue another 30 feet, 300 feet, 3,000 feet, or 30,000 feet. We don’t know. So, all of that gold-bearing rock from depths of 400 to 930 feet was never penetrated by the Carissa mine tunnels. And the low-grade envelope was left completely untouched from the surface to 930 feet. This same shear structure continues along strike for at least 1,000 feet before it narrows. Even so, the shear can be traced 8.5 miles from Willow Creek (42°27'49"N; 108°47'9"W) through the Carissa mine, and all the way to the northern edge of the greenstone belt near Meadow Gulch (42°32'4"N; 108°38'58"W) where it is buried by younger sedimentary rock.

In the mid-1980s, I applied for grants to map South Pass. The entire greenstone belt was wide open with no fences (except around the iron ore mine), and I often went for days, weeks and in some cases, an entire summer without seeing another person. But now there are more man-made structures and fences appearing in the belt. There is even a place called Rock Creek Hollow (42°26'25"N; 108°37'25"W) that didn’t exist when I mapped the greenstone belt. The Hollow has amphitheaters, fire pits, and even a parking lot with a bus turnaround. Near the end of my project, I was actually ran off the road by buses and a flatbed truck filled with portable outhouses. at this area. A barren hillside near this parade, sat a lemonade stand manned by women dressed like pioneers. It is clear that South Pass was changing, and my hope is that the area remains a gold-mining district and some of these people can learn to be friendly and share the road.

The Duncan gold mine and mill as it appeared to me when I first visited South Pass in 1978. I later detected significant gold in a
 distinct fold near the old glory hole. A 2.5 foot long channel sample yielded 0.96 ounce per ton gold!
During my project, I took one Saturday afternoon off to drive to the Mercantile in Atlantic City to have a beer and find out if the world still existed. I met a prospector who was looking for a place to pan for gold: I sent him to Strawberry Creek (42°26'1"N; 108°29'49"W) where he used a man-powered sluice with a hand shovel and managed to stay out of site of the BLM for a month. He was soon chased out of the area even though it was public land. In the fall, he stopped by my office at the University of Wyoming to tell me he had essentially filled his pockets with gold before being chased off of public land. These federal bureaucrats also need to learn to work with people and quit overstepping their bounds. After all, they work for us, not themselves.
Map of the Wyoming province showing locations
of Greenstone belts including South Pass.




As I mapped, I periodically took samples along various shear zones. I noted in between mines, outcrops and prospect pits, most of the shear zone structures were buried under a few inches to possibly a few feet of dirt. Potentially, more than 90% of the gold-bearing structures are hidden. If only I had a way to see through that dirt. Of course there was a possibility of using geophysics, but it would tell me what I already knew - there were miles of gold-bearing shear zones. But, I identified more than a hundred gold anomalies along these structures, and if I could have seen the buried structures, who knows what I would have found? This should give some prospectors some ideas on other placers to search for gold.

A couple of years ago I consulted on a gold placer project at Rock Creek, and it was clear that the 1930s dredging operation did a poor job, missed many areas, and lost a significant part of the gold where it mined. The operation was poorly designed, and even today, one can still find considerable gold (both fine and nuggets) in the dredge tailings.

While mapping, I found chips of rock with alteration characteristic of gold mineralization associated with shear zones elsewhere. These chips were found in the Crows Nest area (42°29'17"N; 108°36’43"W) of the greenstone belt. A short time later, a prospector (Gary Nunn) found several, nice, jewelry grade gold nuggets in the area using a metal detector. So, the Crows Nest also contains hidden shear zones that remain mostly untouched. 

Then there is Willow Creek - likely a very rich placer. But, the state government closed much of this creek to prospecting because it is reportedly filled with mercury! But, there is no known natural source for mercury in the belt; and if there is mercury in the stream, it was accidentally dumped by 19th century mining operations at the Carissa mine, and by now much of it would have worked its way to bed rock and be out of reach of most placer miners. Even more important, if there really is much mercury, it is a finite source that would soon be cleaned up by placer miners. Most of Willow Creek is unprospected and has limited dredge tailings (42°27'49"N; 108°47’9"W).

Many field trips to South Pass were led by the GemHunter to educate the public 
on gold prospecting. These trips were free to the public
Some placers at South Pass contain significant coarse gold. XL Dredging mined portions of Big Atlantic Gulch in about 1910 and recovered nuggets weighing 0.07 to 1 ounce. The ET Fisher Company dredged Rock Creek from 1933 to 1941 and produced 11,000 to 30,000 ounces: 75% of the gold was found within 3 feet of bedrock. Some of the gold was coarse and many nuggets were recovered. Nuggets recovered from Rock Creek include many small nuggets and some large nuggets as well as a boulder that reportedly had 630 ounces of gold.

After five years of mapping, I produced eight 1:24,000 scale geological maps - these should still be available at the Wyoming Geological Survey. I also produced a regional 1:50,000 scale geological map for the pocket of my 129-page book on South Pass published in 1991. This book should be available at the Wyoming Geological Survey. Along with these, I published dozens of books, papers, abstracts and tour guides on South Pass to assist mining companies and prospectors on where to find gold in this region (a partial list of my bibliography is available on my website at http://GemHunter.webs.com), and I wore out a tent, two pairs of field boots, and nearly a dozen tires. It was a dream come true and I feel blessed that I was able to spend so much time at South Pass, meet so many interesting prospectors and few scam artists.   


One of the locals at South Pass

REFERENCES
Hausel, W.D., 1991, Economic geology of the South Pass granite-greenstone belt, Wind River Mountains, western Wyoming: Geological Survey of Wyoming Report of Investigations 44, 129 p.

Hausel, W.D., 1993, Mining history and geology of some of Wyoming's metal and gemstone districts: Wyoming Geological Association Jubilee Anniversary Field Conference Guidebook, p. 39-63.

Hausel, W.D., 1997, The Geology of Wyoming's Copper, Lead, Zinc, Molybdenum and Associated Metal Deposits: Geological Survey of Wyoming Bulletin 70, 224 p.

Hausel, W.D., 2014, A Guide to Finding Gemstones, Gold, Minerals and Rocks: GemHunter’s Books, Amazon, 368 p. 

Hausel, W.D., and Hausel, E.J., 2011, Gold - A Field Guide for Prospectors and Geologists (Wyoming Examples), Self Published, Amazon, 366 p. 

Hausel, W.D., and Hull, J., 1990, Guide to gold mineralization and Archean geology of the South Pass greenstone belt, Wind River Range, Wyoming, in Roberts, S., Geologic field trips to western Wyoming: Geological Survey of Wyoming Public Information 29, p. 178-191.

Hausel, W.D., 1994, Mining history of Wyoming's gold, copper, iron, and diamond districts: Mining History Association 1994 Annual, Reno, Nevada, p. 27-44.

Hausel, W.D., and Love, J.D., 1991, Guide to the geology and mineralization of the South Pass area, in S. Roberts, editor, Mineral Resources of Wyoming: Wyoming Geological Association 42nd Annual Field Conference Guidebook, p. 181-200.

Snyder, G.L., Hausel, W.D., Klein, T.L., Houston, R.S., and Graff, P.J., 1989, Precambrian rocks and mineralization, Wyoming Province: 28th International Geological Congress guide to field trip T-332, July 19-25, 48 p.


A portion of the Radium Springs Quadrangle by the author, showing rocks, mines, veins,
Laramide faults, and shear zones. 
Simplified map of the Lewiston gold district

Simplified geological map of the South Pass-Atlantic City district.

Tailings along Rock Creek, Wyoming