mineral

Moonstone

Orthoclase feldspar ((K,Na)AlSi3O8)

Hardness: 6.0–6.5 (Mohs scale), Color: Colorless to white/gray, Luster: Vitreous to pearly, Crystal structure: Monoclinic, Cleavage: Perfect in two directions, Specific gravity: 2.56–2.59

Hardness: 6

Identified April 23, 2026More mineral →

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Physical properties

Hardness: 6.0–6.5 (Mohs scale), Color: Colorless to white/gray, Luster: Vitreous to pearly, Crystal structure: Monoclinic, Cleavage: Perfect in two directions, Specific gravity: 2.56–2.59

Formation & geological history

Formed from molten rock (magma) that cools slowly indoors; as the magma cools, intergrowths of orthoclase and albite separate into alternating layers, causing the characteristic light play through adularescence.

Uses & applications

Primarily used as a gemstone in jewelry (rings, pendants, earrings) and as a lapidary specimen for collectors or spiritual practices.

Geological facts

The shimmering effect known as adularescence is caused by light diffraction within internal layers of different feldspar minerals. It is the Florida State Gemstone, designated in 1970 to commemorate the Apollo moon landings.

Field identification & locations

Identify in the field by its pearly luster and distinctive blue or white sheen (billowing light) when rotated. Found commonly in Sri Lanka, Madagascar, Brazil, and India. It is distinguishable from glass by its hardness and internal structural planes.