The Yreka occurrence is located at approximately 600 metres in elevation on east facing slopes overlooking Neurotsis Inlet.

At the Yreka occurrence, northwest striking, moderately west dipping calcareous sediments of the Parson Bay Formation overlie Karmutsen Formation tholeiitic basalts, both of the Upper Triassic Vancouver Group. These are overlain by Lower Jurassic Bonanza Group andesitic to rhyodacitic lava, tuff and breccia, which are coeval with, or genetically related to Early-Middle Jurassic Island Plutonic Suite granodiorite occurring as small, isolated plutons.

The Yreka mine lies in skarn-altered limy tuffs. The tuffs, with agglomerates, lenses of limestone and a 30-metre-thick limestone unit form a 300-metre-thick assemblage overlying andesitic lava and underlying andesitic flows and tuffs. These rocks have been folded about a northwest plunging and trending axis. The beds on the southwest limb dip 35 to 55 degrees west. Basalt, diabase and feldspar porphyry dikes have intruded all rocks. A small diorite stock lies nearby on Mount Comstock.

Several northeast trending, ore-localizing faults are indicated, including a major 045 degree striking, 70 degree south dipping shear zone on the New Comstock claim. Lesser steeply dipping 330-degree striking faults contain mineralization.

Epidote-garnet skarn is confined to three stratigraphic horizons and contains most of the mineralization. The skarn is in altered tuff. Limestone beds have been recrystallized but are otherwise unaltered. Mineralization includes pyrrhotite, chalcopyrite and sparse pyrite. Magnetite and specular hematite are locally present.

During 1903 through 1979, a total of 145,334 tonnes of ore, averaging 2.71 per cent copper, 31.22 grams per tonne silver and 0.34 grams per tonne gold was mined (Assessment Report 25797).

Work History

The area was first staked in 1898 with active work continuing until 1903. At this time 2268 tonnes of ore grading 4.5 per cent copper was shipped. In 1917, a new wharf, ore-bunkers and aerial tramway were completed. The same year, 816 tonnes of ore, grading 3 per cent copper, was shipped (Assessment Report 3165).

During 1952 through 1954, Noranda completed programs of surface sampling, geological mapping, geophysical and geochemical surveys and diamond drilling. In 1955 and 1956, 2348 metres of underground development on two levels was completed. In 1965, Minoca and Yreka Mines prepared the property for production. Mining between 1965 and 1967 included the 15 by 49 by 60 metre A zone, grading 3.0 per cent copper (Energy, Mines and Resources Canada Corpfile - Uke Resources Ltd.). Total production for the period totalled 142,052 tonnes, grading 2.9 per cent copper (Assessment Report 3165).

In 1970 and 1971, Green Eagle Mines completed programs of airborne electromagnetic and magnetic geophysical surveys, rock and soil sampling and ground magnetic survey on the area. In 1972, Iso Explorations completed a program of ground geophysical surveys, geological mapping and soil sampling. In 1998 and 1999, Talltree Resources completed programs of rock and soil sampling, geological mapping and a ground electromagnetic survey on the area. During 2015 through 2019, Karmamount Mineral Exploration Inc. completed minor programs of geological mapping and geochemical (rock and soil) and biogeochemical sampling and a 12.9 line-kilometre induced polarization survey on the area as the Yreka property.