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

The author near old Sutherland
mine shaft

The Tin Cup district (also Black Rock-Long Creek district) is located in the western portion of the Granite Mountains (T30 and 31N, R92 and 93W). Find this district by searching 42^o38’53”N; 107^o53’00”W on GoogleEarth or FlashEarth. You will 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 undiscovered jasper, massive sulfide, ruby, sapphire, diamond and other gemstone deposits. If you study the area with aerial photos, many white pegmatitic and gneissic dikes are apparent in the darker country rock. These help to outline some very complex folding: both open and isoclinal folds are evident.

Copper-stained quartzite, Tin Cup

The district includes a group of northeasterly-trending, parallel, shear zones with impressive amounts of jasper, agate, jasperoid and massive sulfides. By following these deposits on the ground, it will become apparent that the barren ground in between the jasper-rich prospect pits contains hidden (or blind) pockets of additional jasper deposits. These jasper deposits are some of the more spectacular jaspers and agates in the State and locally some exhibit impressive tight to isoclinal folds. Many sizable pieces of jasper should be investigated as countertop material. This would make extraordinary counter tops and should provide an enormous resource. Beeler (1907a) and Love (1970) suggested this area also had significant gold anomalies; however, these cannot be duplicated and scattered samples collected from prospects by us contained no detectable gold. At the southern edge of this district is a chlorite-biotite schist and gneiss with spectacular rubies.

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

One poor-quality ruby measured 2.5 inches across. Another stone collected from the Red Dwarf ruby deposit was 90% replaced by zoisite. The original ruby was at least 5 inches in length and retained some high-quality pigeon’s blood red corundum within the large pseudomorph (Hausel and Sutherland, 2000) – thus this deposit potentially hosts some of the largest rubies on earth. Excavation of this deposit and a search of nearby drainages could potentially result in discovery of some impressive specimens of ruby. The district hosts large resources of jasper, some extraordinary rubies and some sapphire and some low-quality jade. Reports of diamonds found in this area that weighed 2 to 5 carats are intriguing (Eugene Clark, personal communication, 1980) and some cryptovolcanic depressions found in this region provides additional intrigue along with drainages named 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 (as dikes) a short time later (Peterman and Hildreth, 1978). The principal mine development in the district was the Sutherland (Red Boy) mine. The Sutherland contains massive pyrite (Hausel, 1989). Beeler (1907a) reported that several gold prospects and one copper prospect in the district yielded gold values from 0.08 to 3.5 opt and up to 15% Cu. These could not be verified, but the mineralization was reported in schist, diorite, quartz veins and jasper.

A group of samples of hematite-stained quartz, cupriferous schist, low-grade banded iron formation and limonite-stained quartz breccia veins 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.

The author stands in prospect pit dug in jasper.

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).