Riebeckite

specimen number:
2062399

location:
St. Peters Dome, El Paso Co., Colorado, USA

description:
Prismatic crystals of black riebeckite embedded up on matrix. Collected in 1977.

St. Peters Dome in El Paso County, Colorado, is a prominent peak within the Proterozoic Pikes Peak batholith, featuring alkali-rich granites and pegmatites that were prospected for rare minerals and fluorite starting in the late 19th century through the mid-20th century, though exact opening and closing dates for individual small workings are largely undocumented. Geologically, the area is famous for hosting the sodium-iron silicate mineral riebeckite, an amphibole that forms dark blue to black prismatic crystals or columnar aggregates within the alkaline Mount Rosa granite.

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