mineral

Calcite

Calcite (CaCO₃), likely crystalline limestone or marble fragment

AI-generated identification · may be incorrect

Pale cream to honey-colored, translucent, with pearly-to-glassy luster and prominent rhombohedral cleavage; Mohs hardness 3, specific gravity about 2.71. The image suggests a rough, cleaved specimen rather than a diagnostic crystal form.

Identified August 14, 2026More mineral →

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Physical properties

Formation & geological history

Calcite precipitates from marine, groundwater, hydrothermal, and metamorphic fluids; limestone deposits commonly formed in Paleozoic–Cenozoic seas, while marble forms by recrystallization during metamorphism. Exact age and host rock cannot be determined visually.

Uses & applications

Used in cement, lime, aggregate, soil treatment, glass, and chemical production; transparent varieties are collected, and optical Iceland spar is used for polarization demonstrations.

Geological facts

Calcite effervesces strongly with dilute hydrochloric acid or vinegar if freshly powdered; it is easily scratched by a copper coin or steel edge. Its double refraction is a notable optical property.

Field identification & locations

Look for rhombohedral cleavage, low hardness, and acid reaction; common worldwide in limestone caves, veins, sedimentary beds, and marbles. Similar pale quartz is harder and lacks cleavage.