mineral

Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: White to pale yellow/honey; Luster: Vitreous to pearly; Crystal structure: Trigonal/Rhombohedral; Cleavage: Perfect rhombohedral in three directions; Specific gravity: 2.71

Hardness: 3 on Mohs scale
Color: White to pale yellow/honey
Luster: Vitreous to pearly

Identified June 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed through sedimentary precipitation in marine environments, hydrothermal veins, or as a primary mineral in igneous carbonatites; found throughout geological time from Precambrian to Holocene.

Uses & applications

Used in the manufacture of cement and mortar, as a soil conditioner in agriculture, in the optical industry (Iceland Spar), and as decorative architectural stone or collector specimens.

Geological facts

Calcite exhibits double refraction; if you look through a clear crystal, images appear doubled. It is the primary component of limestone and marble.

Field identification & locations

Identify in the field using the 'acid test'—it effervesces (fizzes) strongly when in contact with dilute hydrochloric acid. It is commonly found in limestone quarries and cave systems worldwide.