Kochkarite with Gold, Pyrite, Quartz
specimen number:
2062148
location:
Gold Bluff prospect, Marquette Co., Michigan, USA
description: The Gold Bluff prospect, located on the northern shore of the Keweenaw Peninsula within Marquette County, Michigan, is a minor historic exploration site situated along the rugged coastline of Lake Superior. Geologically, the prospect is hosted within the Mesoproterozoic basalts of the Portage Lake Volcanic Series, part of the Midcontinent Rift System. The mineralization occurs as native copper and associated sulfide minerals within quartz and carbonate veins that cut through the basaltic flows. Historically, the site saw limited exploration and small-scale trenching during the mid-to-late 1800s, particularly during the regional copper boom, but it never developed into a major producing mine. Kochkarite is a rare lead bismuth telluride mineral with the chemical formula PbBi4Te7. Geologically, it typically forms in hydrothermal gold-tellurium vein deposits, often occurring as very small, metallic gray to tin-white grains or platy aggregates. It was first described from the Kochkar gold deposit in the Southern Ural Mountains of Russia, where it is found associated with other tellurides, bismuthinite, and native gold. The mineral crystallizes in the trigonal system and is characterized by its high density and metallic luster. Because it often occurs in microscopic quantities, it is primarily identified through electron microprobe analysis or X-ray diffraction. Kochkarite serves as an important indicator of specific geochemical conditions during the final stages of mineral precipitation in high-grade metamorphic or hydrothermal environments.
Tiny metallic kochkarite in a quartz rich matrix with pyrite in tiny masses of native gold. Quite choice for this rare species. Collected in 1999, the identity has been confirmed.
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