mineral

Cat's Eye Moonstone (Feldspar)

Orthoclase (KAlSi3O8) with Albite (NaAlSi3O8) inclusions

Hardness: 6-6.5 (Mohs scale); Color: Pinkish-white; Luster: Pearly to Vitreous; Crystal Structure: Monoclinic; Cleavage: Perfect in two directions at 90 degrees; Chatoyancy (Cat's-eye effect).

Hardness: 6-6
Color: Pinkish-white
Luster: Pearly to Vitreous

Identified March 13, 2026More mineral →

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Physical properties

Hardness: 6-6.5 (Mohs scale); Color: Pinkish-white; Luster: Pearly to Vitreous; Crystal Structure: Monoclinic; Cleavage: Perfect in two directions at 90 degrees; Chatoyancy (Cat's-eye effect).

Formation & geological history

Formed through the slow cooling down of magma (igneous). As it cools, Orthoclase and Albite intergrow in thin, alternating layers. This structure causes light to scatter (adularescence) and, when oriented properly in a cabochon, creates the cat's-eye slit.

Uses & applications

Primarily used in jewelry as cabochon gemstones, beads, and pendants. It is also of high value to gemstone collectors and those interested in holistic mineralogy.

Geological facts

Moonstone is the most famous variety of orthoclase feldspar. The 'cat's eye' effect is called chatoyancy, which occurs when light reflects off microscopic parallel needle-like inclusions within the stone.

Field identification & locations

Identify in the field by its distinct pearly sheen and the movement of the light band when the stone is tilted. It is commonly found in Sri Lanka, India, Myanmar, and Madagascar.

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