Orpiment from Twin Creeks Mine, Nevada, USA

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Collected in the late 1990s, very choice lustrous slightly translucent crystals of orpiment measuring to 0.6 cm in size across the top of matrix. Compared to most of these, this is in very good condition. The Twin Creeks Mine, located in the Potosi District of Humboldt County, Nevada, is a massive Carlin-type gold operation situated along the Getchell Trend. Geologically, the deposit is hosted in Paleozoic sedimentary rocks, specifically the Comus and Antler Peak formations, where gold was deposited by hydrothermal fluids along complex fault zones and fold hinges during the Eocene epoch. The mine is mineralogically significant for producing high-quality crystallized orpiment specimens, featuring large, lustrous orange to deep red-orange crystals that often exhibit a distinct micaceous or foliated habit. Historically, the site was formed through the 1993 merger of the Chimney Creek and Rabbit Creek mines, which had begun operations in the late 1980s. Under the management of Newmont and later the Nevada Gold Mines joint venture, Twin Creeks became one of the most productive gold mines in North America, utilizing both large-scale open-pit methods and advanced autoclaving technology to process refractory ores. While it remains a major industrial producer today, it gained significant attention in the mineral community during the late 1990s when specific pockets in the Vista Pit yielded notable orpiment crystals that are now widely distributed among museum and private collections.