The Tin Cup district in the Sweetwater Rocks, Granite Mountains, Wyoming

The author near old Sutherland
mine shaft

The Tin Cup district (a.k.a. Black Rock-Long Creek district) is in the western part of the Granite Mountains (T30 and 31N, R92 and 93W). Find this district 42^o38’53”N; 107^o53’00”W on GoogleEarth (you can search for Tin Cup Mountain on Google Earth). From high altitude, you should see a large, triangular-shaped, fragment of dark Archean supracrustal rocks with nearby, linear, dark-colored northeasterly-trending mafic (basaltic) dikes. This entire area is complexly deformed and metamorphosed and likely hosts additional undiscovered jasper, massive sulfide, ruby, sapphire, diamond and other gemstone deposits. If you study the area with aerial photos, many white pegmatites (coarse-grain granites) and gneissic dikes are present in the darker country rock. These help to outline many of the complex folds: both open and isoclinal folds are evident. Along with helping to identify cross-cutting faults. The foliation parallel shears and faults are more difficult to pick out on aerial photography, but where prospects line up, there are usually shear zones.

Copper-stained quartzite, Tin Cup

The district includes northeasterly-trending, parallel, shear zones and impressive amounts of jasper, agate, and jasperoid, and some massive sulfides. 

By following these on the ground, it will become apparent there is a lot of barren ground in-between the jasper-rich prospect pits. This area has extensive, hidden (or blind), pockets of additional jasper. These jasper deposits are some of the more spectacular jaspers and agates in the State and locally exhibit impressive tight to isoclinal folds. Sizable cobbles and boulders of jasper should be investigated as countertop and lapidary material. Some would make extraordinary counter tops and provide a new resource for Wyoming. Beeler (1907a) and Love (1970) suggested this area also had significant gold anomalies; however, these cannot be duplicated by the author. However, I only collected scattered samples from prospects and these contained mostly no detectable gold. At the southern edge of this district, is a chlorite-biotite schist and gneiss with some spectacular rubies. One of the ruby deposits was examined by the Dr. Love and the author at different times, and sometime later, Robert Odell (RIP), a Casper Consultant, staked claims on the ruby deposit and named it the Red Dwarf.

Zoisite after ruby from the Red Dwarf schist. Some of the
original ruby is preserved in this specimen.

The Red Dwarf yielded several, large rubies including many zoisite pseudomorphs after ruby that indicate some very large rubies were present in this deposit prior to retrograde metamorphism. One, poor-quality ruby measured 2.5 inches across. Another stone, collected from the Red Dwarf was 90% replaced by zoisite. The original ruby was more than 5 inches in length and about 2 to 3 inches wide,  and retained some high-quality, pigeon’s blood, red corundum in the large pseudomorph (Hausel and Sutherland, 2000). It is possible that this deposit hosts some of the largest rubies on earth. Excavation of this deposit and a search of nearby drainages might produce of some impressive rubies. However, the Red Dwarf has only been examined at the surface. The district also hosts large resources of jasper, other ruby deposits, and some, low-quality, blue and white sapphire, as well as some low-quality jade. Reports of detrital diamonds of 2 to 5 carats, are intriguing, but remain unverified (Eugene Clark, personal communication, 1980). The stones in question were examined by Dr. McCallum at CSU and, according to him, the crystals in question could have been diamonds, but the prospector (Clark) would not let him touch or examine them. Some Cryptovolcanic depressions occur in this region provides additional intrigue along with drainages with names like Diamond Springs Draw.

Map of the Tin Cup district (from
Hausel, 1997).

The district is underlain by amphibolite-grade gneiss, schist and amphibolite metamorphosed at 2,860 Ma. The supracrustal complex was intruded by granite at 2,550 Ma and was followed by intrusion of diabase dikes a short time later (Peterman and Hildreth, 1978). The principal prospect development in the district was the Sutherland (Red Boy) mine. The Sutherland contains massive pyrite (Hausel, 1989). Beeler (1907a) reported several gold prospects and one copper prospect was identified in the district that yielded gold values of 0.08 to 3.5 opt, and as much as 15% Cu. These reported values could not be verified by the author; but, mineralization was reported in schist, diorite, quartz veins and jasper. And there are numerous prospects pits and some trenches in the area, and the author recommends all of these be sampled to try to verify the report by Beeler (1907a).

The author collected some cursory samples of hematite-stained quartz, cupriferous schist, low-grade banded iron formation and limonite-stained quartz breccia. These limited samples yielded 188 ppm to >2.0% Cu, none to 551 ppm Pb, 20 to 253 ppm Zn, 5 to 14 ppm Mo, 20 to 342 ppm As, 0.6 to 14 ppm Sb, none to 0.351 ppm Hg, none to 0.9 ppm Ag, and none to 10 ppb Au (Hausel, personal field notes, 1994).

Reported occurrences

Anderson Mine (SE SE section 13, T31N, R93W). One mile north of Tin Cup Springs. Gold was detected in N80^oE-trending, south-dipping quartz veins in schist (Love, 1970).

Wayne Sutherland point to shear zone
exposed in shaft wall. In background is
a prospect in red jasper

Cedar Rim prospect Location unknown; however, Beeler (1907a) reported a mineralized diorite assayed from 0.01 to 0.02 opt Au.

King Solomon Claim (Section 36, T31N, R92W). Limonite and malachite-stained veins trend northeasterly. Assays of the vein material were reported at 0.1 to 0.88 opt Au (Beeler, 1907a).

Lone Tree claims. Located east of the Queen Sheba claims. A shallow shaft cut a wide ledge of oxidized iron and quartz. Both copper and iron sulfides were noted in the 20- to 30-foot-wide ledge. One sample assayed 15% Cu and 3.5 opt Au (Beeler, 1907a).

Queen Sheba claims. Beeler (1907a) reported this property to lie somewhere on the west end of the district. A shallow shaft was sunk on a huge copper- and iron-stained quartz ledge.

Prospect Pit TC19-95 (NW section 36, T31N, R93W). This prospect lies along a prominent northeast-trending fault in Archean gneiss that was traced on the surface for 5,500 feet (W.D. Hausel, personal field notes). To the northeast, this same structure contains jasperoid and massive sulfides at the Sutherland shaft. Copper mineralization is uncommon along the structure, although weakly copper-stained jasper in the prospect pit contains minor malachite, azurite, tenorite and uncommon chalcocite. A select sample yielded 1.71% Cu, 3.6 ppm Ag, 7 ppb Au, 74 ppm Zn and 10 ppm Pb (Hausel, 1996a).

Some of the extraordinary banded jasper at Tin Cup.
Specimens weighing several hundred pounds were found
in prospect pits and mines in the district.

Prospect Pit TC27-95 (NE section 26, T31N, R93W). Samples of fault breccia from this prospect pit contain goethite, limonite, trace azurite and minor jasper with calc-silicate veinlets. A sample of the breccia assayed 0.48% Cu, 0.5 ppm Ag, and a trace of lead and zinc (Hausel, 1996a).

Prospect Pit TC28-95 (NE section 26, T31N, R93W). A short distance to the west of TC27-95, minor copper stains were found in breccia. A select sample yielded 0.29% Cu and a trace of lead and zinc (Hausel, 1996a).

Prospect Pit TC41-95 (NW section 19, T31N, R92W). Butterscotch and red jasper has vugs filled with botroyoidal quartz in graphitic schist. A sample of schist with jasper yielded 0.13% Cu, 694 ppm Zn, 43 ppm Pb, 11 ppm Mo and 86 ppm As (Hausel, 1996a).

Prospect Shaft TC42-95 (NW section 19, T31N, R92W). One thousand feet to the northeast of TC41-95 is a shallow 8-foot deep prospect that exposed granular quartz in an iron-stained schist. A sample of the schist yielded 0.22% Cu, 336 ppm Zn, 26 ppm Pb, 38 ppm Mo and 65 ppm As (Hausel, 1996a).

Red Boy (Sutherland) Mine (Section 36, T31N, R93W). Massive pyrite is found in hematitic iron formation that was exposed in a shaft. According to the Prosepctus of the Emigrant Mining Company (June 12, 1938) samples from this mine assayed 0.04 to 0.46 opt Au. Samples collected from the bottom of the shaft contained 0.4 opt Au and 23 opt Ag (Love, 1970). Several samples of the massive pyrite were collected to verify these results, in 1983, but none contained detectable gold suggesting that the earlier assays may be questionable (W.D. Hausel, personal field notes).

Mining Districts and Mineralized Terrains (after Hausel, 1997).