Knob Hill Mine, Republic Mining District, Ferry County, Washington, USAi

Regional Level Types
Knob Hill Mine	Mine
Republic Mining District	Mining District
Ferry County	County
Washington	State
USA	Country

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West 1/2 of the Southeast 1/4 of section 27, T37N-R32E.

A Au-Ag mine located at the Head of Eureka Gulch. It worked 4 parallel epithermal veins and a cross vein with widths from 5'-15' in Eocene volcanics of the Klondike Mountain Formation.

Developments include a 1,200' shaft with 9 levels at 110' intervals, The golden promise shaft, adjoining rad tunnel connecting the two mines, and abandoned open pits.

The mine produced more then $10,000,000 by the end of 1951, on June 24, 1989 the Hecla mining company produced the 2,000,000th ounce of gold from the Hecla 2 shaft.

Production records up to 1985 list the mine as producing just over 3,200,000 tons of ore.

Note: There is some confusion with this mine in Cannon (1975). Cannon lists "Day Mine" as a distinct mine. However, thorough research fails to show a "Day Mine" but Day Mines was a company that operated the Knob Hill among other mines. None of the other mines operated by the company have sylvanite described, so it is fair to say that Cannon duplicated the Knob Hill Mine as the "Day Mine".




Structure: The Republic Graben Trends Northeasterly And Is Bounded On The West By The Bacon Creek Fault And On The East By The Sherman Creek Fault. Eureka Fault System.

Alteration: Propylitization And Silicification. See Geology Comments.

Commodity: Aprox. 40% of Au occurs As free grains of electrum, the remainder probably As selenides and tellurides. The principal ore mineral of Ag is naumannite. The au:ag ratio ranges 1:1.5 to 1:9, averages 1:5, and usually decreases with depth by increase in Ag grade.

Deposit: Two vein types are recognized: 1) shear veins - long dimension is along strike, short dimension is down dip, narrower than dilational veins, generally host lower grade ore, strike nw, example is bailey vein. 2) dilational veins - long dimension is down dip, short dimension is along strike, wider than shear veins, generally host higher grade ore. This record has been merged with sp00082, which has been deleted.

Deposit type: Epithermal vein, Comstock

Development: Mill.cap: 270 tpd ; econ.com: in 1990, cash cost of production was $130 per oz. Of Au and full cost of production was $150 per oz of au. Studies were scheduled for 1991 on whether increased reserves would justify an increase in the mill's 270 tpd capacity.

Geology: Alteration comments: propylitization and silicification. Amphiboles altered to chlorite-carbonate, feldspars altered to sericite and carbonate. Silicification is predominant proximal to upper level veins. Geology comments: golden promise veins occur between two right lateral strike slip faults, the hermes shear and the crosby shear, known in mine usage As the "shear couplet". Black chalcedony associated with the the golden promise no. 1 vein is unique in the district. In the golden promise veins, vein textures range from banded to colliform to botryoidal to "baroque" (mine term for a flowery, ornate texture associated with the highest grades). The nearby stewart, mountain lion, and mud lake pits are hosted in part by volcaniclasic sediments (lowermost klondike mountain formation?) and are associated with argillization and hydrothermal brecciation.

Rock formation(s): Sanpoil Volcanics;Knob Hill Stock


Ore(s): Gold Deposition Is Believed To Be Genetically Connected With The Intrusion Of The Quartz Latite Porphyry Stock. Dextral Strike Slip Movement On The Eureka Fault System Is Believed To Have Created The Shears And Dilational Zones Which Were Subsequently Mineralized. Flexures Or "Rolls" In The Veins From Steeper To Flatter Dips Are Very Important Controls Of High Grade Ore. Ore Is Hosted Mainly By Sanpoil Volcanics, With Minor Amounts Of Ore In The Knob Hill Stock.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

31 valid minerals.

Rock Types Recorded