Calcite

specimen number:
2063664

location:
Holbrook Mine, Bisbee, Arizona, USA

description:
A loose floater grouping of curving stalactitic lustrous translucent calcite crystals without matrix. This is in terrific condition all around. The specimen comes with a previous label from the collection of Ray DeMark.

The Holbrook Mine, located in the Warren Mining District near Bisbee in Cochise County, Arizona, began operations in the late nineteenth century and became one of the foundational underground copper mines of the region. Sunk into Paleozoic limestone formations that had undergone extensive hydro-thermal alteration and faulting, the mine produced substantial amounts of rich copper ores like malachite and azurite while breaking into large natural karst caverns. Within these protected underground cavities, miners and early mineral collectors discovered extraordinary specimens of helictic calcite, a peculiar speleotherm form of calcium carbonate. Unlike typical stalactites that hang straight down due to gravity, these helictic formations feature delicate, twisting, worm-like branches that grow in random directions, driven by capillary action and hydrostatic pressure pushing mineral-rich fluids through microscopic central channels. While active mining at the Holbrook shaft ceased in the early twentieth century as operations consolidated, specimens of helictic calcite from its early cavern openings remain celebrated historic treasures among mineral enthusiasts.

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