Blue Star Mine, Lynn Mining District, Eureka County, Nevada, USAi

Regional Level Types
Blue Star Mine	Mine
Lynn Mining District	Mining District
Eureka County	County
Nevada	State
USA	Country

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Produced $1.4 million (period value) in turquoise. Subsequently, was discovered as a Carlin-type gold deposit.

Deposit: Gold, copper, gemstone prospect located along prospect ridge; info.src: 1 pub lit.

Development: Located along prospect ridge.

Rock formation(s): Hamburg Dolomite.

Structure: Roberts Mountains Thrust.

Alteration: Sericitic, Argillic.

Commodity: Arsenic and gold were the most effective surface geochemical indicators.

Deposit: Nodular turquoise forms lenses and seams along quartz veins in altered dikes and along faults. Au mineralization is partly hosted by upper plate rocks, and is accompanied by abundant Cu mineralization with little carbonaceous material. In the upper pit, NW of the mine, disseminated Au mineralization occurs along a steep N20E fault, with the highest grade ore localized at the intersection of an older E-W fault and a younger N-S fault. First production year: 1929 (turquoise); 1960 (Au) discovery year: 1929 (turquoise); 1959 (Au).

Deposit type: Carbonate-hosted Au-Ag.

Development: Small bodies of gem-grade turquoise were discovered and developed in 1929 at the Number Eight mine along the ridge forming the west edge of Little Boulder Basin, about 0.75 mile (ca. 1,207 m) east of the Blue Star mine. Total turquoise production since 1929 is estimated at $1,500,000 (period value). Au was discovered in 1959 at the Number Eight mine along the Roberts Mountains thrust. A 100 ton cyanide mill was erected on the property in 1960 and was operated in a small way until 1962. Kerr-Mcgee Oil Industries purchased the property in 1964. Newmont acquired the Blue Star turquoise property in 1968. Exploration drilling identified reserves of 1.6 million tons/0.12 opt Au in three orebodies. Open pit mining began in 1974 at Blue Star; econ.com: there is a 10:1 ratio of heap leach ore to mill ore at Blue Star. 1,654 holes totalling 850,000 ft (ca. 259 km) have been drilled as of April 1990 to define orebodies at Blue Star and the nearby Genesis Mines.

Geology: Copper mineralization appears to predate the gold deposition. Turquoise was concentrated along quartz veins in altered dikes and along faults cutting the thinly bedded shale, siltstone, and chert. The turquoise was nodular, forming lenses and seams. 10% was gem quality (Morrissey 1968). Gold has been recognized as discrete grains 1 to 13 microns, at the borders of detrital quartz grains and within quartz overgrowth on detrital grains. Gold in mineralized dikes was associated with sericite. A large portion must be less than 0.5 microns and unrecognized. Vinini formation: most favourable host rocks are sandy siltstones, quartzite sandstones also work well As hosts. The limestones are poor hosts without extensive hydrothermal ground preparation. Dacite porphyry dikes & quartz diorite outcrop to the west and north. The diorite was dated as 121 million years. Both are strongly altered, with argillic and sericitic assemblages recognized. Unaltered post-mineralization rhyolite porphyry was encountered in drill holes in the mine area.

Rock formation(s): Vinini Formation.

Ore(s): Orebodies are located on the west limb of a north-trending anticlinal structure which is cut by E-, NE-, and NW-trending normal faults. Orebodies are restricted to strongly fractured, near E-W high angle faults and a NE-trending dike swarm. The south and east orebodies lie immediately below the Roberts Mountains thrust, while the north orebody lies directly above the thrust. Igneous dikes host a minor amount of ore.

Commodity List

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

Mineral List

18 valid minerals.

Rock Types Recorded