Mining districts and mineralized terrains of Wyoming
(after Hausel, 1997; and Hausel & Hausel, 2011).
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)
|Folded BIF from the Atlantic City iron ore mine, Wyoming, with |
|Copper-stained BIF from the Seminoe Mountains greenstone belt, |
Wyoming, with both black and white quartz veinlets
mixed with dark gray magnetite.
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.
|The Duncan mine and mill, 1989|
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!
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
|One of the locals at South Pass|
|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|