
mineral
Calcite–fluorite mineral specimen with iron-oxide staining
Calcite (CaCO₃), likely fluorite (CaF₂), with possible quartz and iron/manganese oxides
AI-generated identification · may be incorrectWhite, translucent, bladed to rhombohedral crystals form a crust around green, pink, and brown matrix. Calcite has Mohs hardness 3, vitreous to pearly luster, rhombohedral cleavage, and effervesces in dilute acid; fluorite is harder (Mohs 4), commonly cubic, and may fluoresce under UV light.
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Physical properties
White, translucent, bladed to rhombohedral crystals form a crust around green, pink, and brown matrix. Calcite has Mohs hardness 3, vitreous to pearly luster, rhombohedral cleavage, and effervesces in dilute acid; fluorite is harder (Mohs 4), commonly cubic, and may fluoresce under UV light.
Formation & geological history
Likely a hydrothermal vein specimen formed when mineral-rich fluids deposited carbonate and fluorite in fractures, with later oxidation producing the reddish-brown staining. Exact age and locality cannot be determined from the image.
Uses & applications
Primarily a collector specimen; calcite and fluorite are important industrial minerals used in cement, lime, steelmaking, optics, and chemical processing.
Geological facts
The contrasting green, pink, white, and rusty colors probably reflect multiple mineral phases rather than a single colored mineral.
Field identification & locations
Look for calcite cleavage and acid reaction, fluorite’s cubic cleavage or UV fluorescence, and possible quartz’s glassy, non-cleaving grains. Common sources include Mexico, China, the United States, and Morocco.