1.9" Gypsum on Dogtooth Calcite Crystal Cluster - China

This is a cluster of red-orange scalenohedral calcite crystals collected from China. Colorless gypsum var. selenite crystals encrust many of the calcite crystals.

About Calcite Crystals

Calcite crystals are a form of calcium carbonate (CaCO₃) known for their diverse shapes, transparency, and vibrant range of colors. They typically form in rhombohedral, scalenohedral, or prismatic shapes, often with well-defined, sharp edges and glossy surfaces. Calcite crystals are often translucent or transparent, sometimes displaying a double refraction effect where objects viewed through the crystal appear doubled. They can appear in various colors—white, clear, yellow, pink, blue, green, and orange—depending on impurities or trace minerals.

A notable characteristic of calcite is its reaction with weak acids like vinegar, which causes it to effervesce, or fizz, as it releases carbon dioxide. This property makes calcite crystals a key tool in geological identification and studies. Calcite forms in many environments, from sedimentary rocks like limestone and marble to hydrothermal veins.

Selenite is a variety of gypsum, a soft sulfate mineral composed of calcium sulfate dihydrate (CaSO4 · H2O). When chemically pure, gypsum is transparent and colorless, but impurities give the gypsum a diverse range of colors and formations. Desert rose selenite and satin spar are just a few of the varieties of gypsum known to have formed though hydrothermal processes.
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DETAILS
SPECIES
Calcite & Gypsum var. Selenite
LOCATION
China
SIZE
1.9 x 1.2"
CATEGORY
ITEM
#146693