mineral

Calcite

Calcite (CaCO₃), likely massive crystalline calcite

AI-generated identification · may be incorrect

Usually white to cream with pearly-to-glassy luster; Mohs hardness 3, perfect rhombohedral cleavage, and commonly translucent. It effervesces vigorously in dilute hydrochloric acid or strong vinegar, though vinegar may react slowly.

Identified August 17, 2026More mineral →

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Physical properties

Formation & geological history

Forms in limestone, marble, hydrothermal veins, caves, and evaporite environments through precipitation or recrystallization. Calcite occurs from ancient Precambrian rocks to modern cave deposits; the specimen’s exact age cannot be determined visually.

Uses & applications

Used in cement, lime, aggregate, glass, agriculture, and chemical production; transparent crystals are collected and occasionally cut as decorative specimens. This rough piece has modest commercial value.

Geological facts

Calcite is one of Earth’s most abundant minerals and has several crystal habits, including rhombohedra, scalenohedra, fibers, and massive forms. Double refraction is visible through clear crystals.

Field identification & locations

Common worldwide, especially in limestone regions, Mexico, Iceland, the United States, and China. Confirm with its softness, rhombohedral cleavage, and acid reaction; it can be distinguished from quartz because quartz scratches calcite.