mineral

Calcite Rhomb

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Creamy white to pale yellow; Luster: Vitreous to pearly; Crystal Structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions; Specific Gravity: 2.71

Hardness: 3 on Mohs scale
Color: Creamy white to pale yellow
Luster: Vitreous to pearly

Identified June 29, 2026More mineral →

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Physical properties

Formation & geological history

Formed through sedimentary precipitation in marine environments or hydrothermal veins. This specimen likely originated from a larger crystalline mass that was cleaved into a rhombohedral shape.

Uses & applications

Used as a major component of cement and mortar in construction, as a soil conditioner in agriculture, and as a decorative mineral specimen for collectors. Transparent varieties are used in optical instruments.

Geological facts

Calcite is famous for its double refraction (birefringence); if you place a clear piece over text, it will appear as two images. It is the primary mineral found in limestone and marble.

Field identification & locations

Identifiable by its 75-degree rhombohedral cleavage and its strong effervescent reaction to dilute hydrochloric acid. Commonly found in limestone quarries and cave systems globally.