Cortez Silver Mine (Garrison; Arctic; St. Lows; Mt. Tenabo; Fitzgerald; Cortez Metals Mine), Cortez Mining District, Eureka County, Nevada, USAi

Regional Level Types
Cortez Silver Mine (Garrison; Arctic; St. Lows; Mt. Tenabo; Fitzgerald; Cortez Metals Mine)	- not defined -
Cortez Mining District	Mining District
Eureka County	County
Nevada	State
USA	Country

Structure: Deposit In Window Of Roberts Mtn Thrust

Alteration: Dikes Highly Altered To Kaolin, Calcite, Sericite, Quartz.

Deposit: Prospectors from austin located the first claims in 1863 on the st. Louis vein. George hearst was one of the original owners of the property. In 1869 the first mill was built, principle early production was from the garrison and arctic lodes. The cortez metals co., owns the properties formerly held by the tenabo mill and mines co. Underground workings total over twenty miles. 2 kinds of ore bodies: 1) blanket and pipe replacement mantos in dolomite 2) fissure veins localized near dikes

Deposit type: Polymetallic replacement

Development: George hearst was one of the original owners of the property. First mill built in 1869. Cortez gold mines co. Owns the properties for merly held by the tenabo mill and mines co.

Geology: Most of the ore bodies were in the hamburg dolomite; locally they did extend across the quartzite, with some ore in the basal part of the hansen creek limestone. The ore bodies were of two kinds: 1) blanket & pipe replacement mantos in the dolomite 2) fissure veins localized along or near dikes. The mantos were far more productive, the replacement was highly irregular and localized by obscure factors (nasursky & gilluly). Fissure veins were only profitable in the upper oxidized levels, gold was associated with pyrite and averaged .15 oz/t. The quartz porphyry dikes trend generally w-nw., they are no W mainly kaolin, quartz, sercite, & calcite. The dikes were sheeted soon after they solidified and the fissures filled with banded sulfide ore. The country rock nearby was metamorphosed to a quartz, calcite, tremolite, actinolite,orthoclase, sericite, and biotite paragenesis (emmons w.h. 1910). Grade averaged 70-90 opt silver.

Rock formation(s): Hamburg Dolomite;Eureka Quartzite;Hansen Creek Limestone


Ore(s): Fissures In Dikes; Carbonates And Quartzite Next To Dikes.

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Link to USGS MRDS:	10044681

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