mineral

Calcite crystal cluster

Calcite (calcium carbonate, CaCO₃), likely honey or amber calcite

AI-generated identification · may be incorrect

Large translucent cream-to-golden crystals with prominent rhombohedral cleavage and pearly-to-glassy luster; Mohs hardness 3, specific gravity about 2.71. The dark attached material may be matrix or a separate sulfide-bearing mineral, possibly pyrite or galena, but cannot be confirmed visually.

Identified August 24, 2026More mineral →

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Physical properties

Formation & geological history

Calcite commonly forms from hydrothermal fluids, caves, and carbonate-rich sedimentary rocks. The specimen’s exact age and locality cannot be determined from the photograph; the Paris region is dominated by younger sedimentary limestones where calcite is geologically plausible.

Uses & applications

Used in cement, lime, aggregate, optical instruments, and chemical processing; attractive crystal clusters are collected and occasionally displayed as decorative specimens.

Geological facts

Calcite strongly effervesces with dilute hydrochloric acid and shows excellent cleavage. Transparent varieties can display double refraction, while honey calcite owes its color to impurities or inclusions.

Field identification & locations

Identify by its rhombohedral cleavage, softness, and vigorous acid reaction; it will scratch easily with a steel knife and should not be cleaned with strong acid. Common sources include Mexico, Morocco, the United States, China, and European carbonate deposits.