CALCITE WITH HEMATITE

ABOUT THE SPECIMEN

Calcite from Tsumeb comes in all shapes and colors, with one of the most recognizable varieties being those included with rich, earthy red hematite. This is a nice, large, and dense cluster, featuring blocky crystals showing different growth formations, as well as some thinner, lenticular crystals stacked into a tower of sorts. The inclusions are nicely dispersed and plainly visible, and it’s in great condition for what it is!

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Tsumeb's hematite-included calcite forms in the oxidation zones of the mine's unique pipe structure, where groundwater penetrated deeply through karstic dolomite to depths exceeding 800 meters. The specimens typically display sharp rhombohedral crystals, ranging from translucent to deeply opaque, colored brick-red to ruddy brown by microscopic hematite grains dispersed throughout the calcite structure. Some pieces show phantom zoning where hematite accumulated on earlier growth surfaces before being overgrown by clear calcite, while others contain uniformly disseminated inclusions that completely saturate the crystals. What makes these geologically interesting is their formation context - they crystallized from carbonate-rich solutions in vuggy oxidation zones, with the hematite derived from weathering of iron-bearing primary sulfides like pyrite. The color intensity varies significantly based on hematite concentration, creating a spectrum from salmon-tinted specimens to examples so heavily included they're nearly opaque. Tsumeb produced calcite in extraordinary variety due to the mine's three separate oxidation zones and complex paragenesis, but the hematite-included pieces remain distinctive for their characteristic "chocolate calcite" appearance when heavily saturated with inclusions.