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Tomichi District, Gunnison Co., Colorado, USA

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Location is approximate, estimate based on other nearby localities.
Latitude & Longitude (WGS84): 38° North , 106° West (est.)
Margin of Error:~43km
Köppen climate type:Dfc : Subarctic climate

Also known as White Pine district.
12 miles SSE Sargents. Pb, Ag, Zn, Cu, Au, Fe.

The early production from the Tomichi district was principally oxidized silver and lead ore, but later primary lead and zinc ore became the most valuable. Although some gold, silver, and copper are recovered, the district now primarily produces zinc and lead. A small tonnage of iron ore was obtained many years ago from a magnetite deposit at the Iron King mine, northeast of Whitepine.

The ore deposits vary considerably in metallic content, mineral assemblages, form, and occurrence. In general, however, the deposits in the Paleozoic sedimentary rocks are of the replacement type in limestone and dolomite; those in all the other rocks are fissure veins. The vein deposits occur in the northern two-thirds of the district and continue north of Brittle Silver Basin into the Chalk Creek district. The chief replacement deposits lie east of Whitepine in an area of about 1 square mile in the northwest half of the patch of folded and faulted strata of Paleozoic age preserved in a syncline. Most of the past mining operations in the district were concentrated in the area east of Whitepine, and in another
area 2 miles northeast, near the junction of Deer Gulch and Tomichi Creek. Of the many mines in the district, only five were accessible, even in part, at the time of this investigation.
Among the vein deposits only the pyritic quartz veins are of significant economic importance, although a few quartz-fluorite veins occur in the northern part of the district. The pyritic quartz veins range from irregular stringers a fraction of an inch wide to well-defined veins 6 feet thick, but most of those on which mines are located are from 1 to 4 feet thick. Some extend a hundred feet or less, but others attain a length of about half a mile. Although the attitudes of the veins vary considerably, most veins have a northerly strike and steep westerly dip, and most are in the Mount Princeton quartz monzonite. The vein filling is typically white vuggy quartz and sparse to very abundant pyrite, some chalcopyrite, and local shoots of galena and sphalerite. The galena is commonly si1ver-bearing; gold reportedly occurs in some of the pyrite and in native form in some of the oxidized ore. Several other minerals occur locally, as greenockite, chalcoite, azurite, malachite, tennantite, tetrahedrite, anglesite, cerussite, and native silver. Barite occurs in the quartz gangue of the Lilly and Bill Short mines.
The depth of oxidation is not known precisely but is not great, as indicated by fresh sulfides in the vein quartz exposed in many shallow prospect pits. The information available indicates that none of the mines on veins were more than a few hundred feet deep.

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Mineral List

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52 valid minerals.

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U.S. Geological Survey Professional Paper 289
USGS OFR 56-103

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