mineral

Optical Calcite

Calcium Carbonate (CaCO3)

Hardness: 3 on Mohs scale; Color: Colorless to white; Luster: Vitreous to pearly; Crystal System: Trigonal; Cleavage: Perfect rhombohedral in three directions; Optical Property: High birefringence (double refraction).

Hardness: 3 on Mohs scale
Color: Colorless to white
Luster: Vitreous to pearly

Identified July 9, 2026More mineral →

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Physical properties

Formation & geological history

Forms through chemical precipitation in sedimentary environments or as a secondary mineral in igneous hydrothermal veins and metamorphic limestone/marble deposits.

Uses & applications

Used in optics for polarizing filters, as a source of lime in cement, and as a decorative specimen for collectors interested in physics and mineralogy.

Geological facts

Also known as Iceland Spar, this mineral was used by Vikings for navigation (the Sunstone) and is famous for its ability to split a beam of light, making objects appear doubled when viewed through it.

Field identification & locations

Identify by its rhombohedral shape (like a slanted cube) and its reaction (effervescence) to weak hydrochloric acid. Look for the distinct double image effect when placed over text.