Eldorado Bar deposit (Eldorado Strip Mine), Eldorado Bar, East Helena, Lewis and Clark County, Montana, USA (original) (raw)

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The great quantity of sapphires was recovered from channels in Eldorado Bar, approximately 19 km NE of Helena. Sapphire-bearing pebble-gravel deposits are located on high terraces, 30 to 60 m above the Missouri River. The channel thicknesses locally reach 10 to 12 m. Gold, almandine-pyrope garnet, kyanite, topaz, cassiterite, chalcedony, and pseudomprphs of limonite after pyrite occur with sapphire.

Ref: E.Ya. Kievlenko (2003) Geology of gems, p. 70

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