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Quartz Hill, Central City District, Gilpin Co., Colorado, USA

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Latitude & Longitude (WGS84): 39° 47' 21'' North , 105° 31' 46'' West
Latitude & Longitude (decimal): 39.78927,-105.52966


INTRODUCTION - Pitchblende was produced intermittently in the Central City district from 1872 to about 1916. The ore, some of which contained as much as 70% U3O8, came chiefly from four veins, the German-Belcher, the Kirk, the Wood and the Calhoun. Although few production figures are available, it is estimated that several hundred tons of uranium ore has been shipped from the district.

GEOLOGY - The pitchblende bearing veins on Quartz Hill are, for the most part, in medium-grained granite gneiss of pre-Cambrian age. The gneiss is light to medium gray on fresh surfaces and weathers to a reddish brown. The gneiss is exposed in an area about 4 miles long and 1.5 miles wide and is surrounded by quartz-biotite schist of the Idaho Springs formation.

ORE DEPOSITS - Most known pitchblende deposits in the Central City district are on Quartz Hill in an area half a mile square. These deposits occur in gold and silver bearing veins that follow east or northeast striking faults. Pitchblende occurs in small lenses, streaks and stringers mostly on the hanging-wall side of the veins. In the Kirk mine, which contained the largest known deposit in the area, pitchblende was distributed through a vertical distance of 350 ft, but most of the ore, some containing as much as 70% to 80% uranium was found in the upper 250 ft.

Mineral List

Mineral list contains entries from the region specified including sub-localities

22 valid minerals.

Rock Types Recorded

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Rock list contains entries from the region specified including sub-localities

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Alphabetical List Tree Diagram

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Paleoproterozoic
1600 - 2500 Ma
Felsic and hornblendic gneisses, either separate or interlayered

Age: Proterozoic (1600 - 2500 Ma)

Description: Includes metabasalt, metatuff, and interbedded metagraywacke; locally contains interlayered biotite gneiss. Derived principally from volcanic rocks

Lithology: Major:{gneiss}, Minor:{metabasalt,metagraywacke}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Paleoproterozoic
1600 - 2500 Ma
Quartz-feldspar gneiss

Age: Proterozoic (1600 - 2500 Ma)

Description: Gray, dark-gray, white, pinkish-gray, and tan, moderately foliated to well-foliated, layered, fine- to coarse-grained (mostly medium grained) quartz-plagioclase-microcline-biotite gneiss. Proportion of minerals varies widely. Layers typically 10 cm to several tens of meters thick and commonly wavy. Locally contains layers of foliated monzogranite and granodiorite. May contain minor, thin layers of hornblende gneiss and amphibolite. Commonly migmatitic. U-Pb date on weakly foliated rock of monzogranitic composition in northwestern part of Indian Hills 7.5-minute quadrangle is 1,776±4 Ma. Weathers tan to pinkish tan in rounded outcrops. Crops out widely throughout map area

Reference: Kellogg, K.S., Shroba, R.R., Bryant, Bruce, and Premo, W.R. Geologic Map of the Denver West 30' x 60' Quadrangle, North- Central Colorado. USGS Geologic Investigations Series 3000. [35]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License


Localities in this Region


This page contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

Moore, F. B. and C. R. Butler (1952), Pitchblende Deposits at the Wood and Cahoun Mines Central City Mining District, Gilpin County, Colorado.

Sims, P.K. and others (1963) Geology of Uranium and Associated Ore Deposits Central Part of the Front Range Mineral Belt Colorado. U.S. Geological Survey Professional Paper 371, prepared on behalf of the U.S. Atomic Energy Commission.

Eckel, Edwin B. (1997), Minerals of Colorado, updated & revised.

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