mineral

Calcite crystal aggregate

Calcite (CaCO₃), likely cave or hydrothermal carbonate formation

AI-generated identification · may be incorrect

White to cream, pearly-to-glassy luster with abundant bladed or scalenohedral crystals; Mohs hardness 3, excellent rhombohedral cleavage, trigonal crystal system, and specific gravity about 2.71. It commonly effervesces vigorously with dilute hydrochloric acid.

Identified September 18, 2026More mineral →

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Physical properties

Formation & geological history

Forms by precipitation from carbonate-rich groundwater, cave fluids, or hydrothermal solutions, often coating cavities and fractures in limestone or volcanic rock. The specimen’s exact geological age cannot be determined from the image.

Uses & applications

Used industrially for cement, lime, aggregate, and chemical production; clear crystals are collected but are generally not gemstone-grade. Attractive cabinet specimens may have modest collector value.

Geological facts

Calcite is strongly birefringent, producing doubled images when viewed through a clear crystal. Crystal habit and color can vary substantially with impurities and growth conditions.

Field identification & locations

Identify it by its soft, easily scratched surface, rhombohedral cleavage, acid reaction, and commonly white bladed crystal clusters; common worldwide in limestone caves, veins, and geodes. Avoid relying on appearance alone because aragonite and gypsum can look similar.