Ethel Mine, Index Mining District, Snohomish County, Washington, USAi

Regional Level Types
Ethel Mine	Mine
Index Mining District	Mining District
Snohomish County	County
Washington	State
USA	Country

The Ethel Mine was originally staked around the turn of the century and closed around 1920. It worked a shear zone in granodiorite from a few inches to 27' in width. The primary ore minerals were Bornite and Chalcopyrite, and the mine averaged around 4% Cu. It assayed as high as 77 oz of silver per ton and over 50% Copper, although these assays must have been taken from very narrow seams of pure Bornite. The high assays caused a rush of investors and the quick development of the mine even though the ore shortly pinched out at depth. The mine was developed by 4 adits consisting of 3200' of tunnel, and was equipped with a 80 ton pelton wheel-powered mill, electric lighting plant, and aerial tramway. It produced 400 only tons of ore from 20 years of on and off mining. There were attempts to re-open the mine during the second world war but this did not succeed.

Structure: Rocks Of The Area Include Various Accreted (Melange) Terranes And Batholithic Rocks Representing Early Igneous Activity Of The Cascade Magmatic Arc.

Geology: The country rock is granodiorite of the index batholith (tabor and others, geol. Map, p. 10) which is cut by narro W dikes of granodiorite porphyry (weaver, 1912, p. 76).

Ore(s): Ore Occurs In A Shear Zone That Ranges From A Few Inches To 27 Ft. Wide (Broughton, 1942, P. 15). Weaver (1912, P. 76) Describes The Mineralization As Irregularly Distributed In Lenses Accompanied By Considerable Amounts Of Crumbly Granite Resembling Arkose.

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Link to USGS MRDS:	10056098

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References