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Tomichi District, Gunnison Co., Colorado, USA

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.

References

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

Mineral List

Mineral list contains entries from the region specified including sub-localities
Acanthite
Actinolite
'Amphibole Group'
Anglesite
Aragonite
var: Zincian Aragonite

Arsenopyrite
Autunite
Azurite
Baryte
'Calamine'
Calcite
Cerussite
Chalcocite
Chalcopyrite
Chlorargyrite
'Chlorite Group'
Chrysocolla
Copper
'Copper Stain'
Cuprite
Diopside
Dolomite
Enargite
Epidote
Euxenite-(Y)
Fluorite
Gahnite
Galena
var: Argentiferous Galena
'Garnet'
Gold
Greenockite
Hematite
var: Specularite
Hemimorphite
Kaolinite
Limonite
Magnetite
Malachite
Molybdenite
Muscovite
var: Sericite

'Olivine'
Parsonsite
Phlogopite
Polycrase-(Y)
Pyrite
Quartz
'Serpentine Group'
Siderite
Silver
Smithsonite
Sphalerite
Stephanite
Tennantite
Tetrahedrite
Topaz
Torbernite
Tremolite
Uraninite
'Wad'
Xenotime-(Y)
Zircon


68 entries listed. 49 valid minerals.

Localities in this Region

USA
USA

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Copyright © Jolyon Ralph and Ida Chau 1993-2011. Jobs in Colorado, USA Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them.Further information contact the Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of hundreds of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register. Current server date and time: 19th Jun 2011 22:27:12
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