mineral

Moonstone (specifically Cat's Eye or Gray Moonstone)

Orthoclase (Potassium Aluminum Silicate) with the formula (K,Na)AlSi3O8

AI-generated identification · may be incorrect

Hardness: 6.0-6.5 on Mohs scale. Color: Gray, brown, and silvery-white. Luster: Vitreous to pearly. Crystal Structure: Monoclinic. Cleavage: Perfect in two directions. Special Property: Chatoyancy (cat's eye effect) and adularescence.

Hardness: 6
Color: Gray, brown, and silvery-white
Luster: Vitreous to pearly

Identified March 25, 2026More mineral →

Explore Moonstone (specifically Cat's Eye or Gray Moonstone) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks, specifically within pegmatites. The visual effect is created by the intergrowth of two types of feldspar (orthoclase and albite) that separate as the magma cools, creating thin alternating layers.

Uses & applications

Primarily used in jewelry (cabochons, rings, pendants) and as a highly sought-after metaphysical stone for collectors.

Geological facts

Ancient Romans believed moonstone was formed from frozen rays of moonlight. It is the Florida State Gemstone, even though it is not naturally found there (intended to honor the moon landings).

Field identification & locations

Identify in the field by its pearly sheen and 'schiller' effect when rotated under light. Major deposits are found in Sri Lanka, India, Myanmar, and Madagascar. Collectors should look for a sharp 'eye' or intense adularescence.