mineral

Moonstone

Orthoclase (Potassium Feldspar), (K,Na)AlSi3O8

Hardness of 6 on the Mohs scale; colors range from colorless, white, peach, gray, to green with a characteristic pearly to vitreous luster and adularescence (a floating shimmer of light); monoclinic crystal system; distinct cleavage in two directions at nearly 90 degrees; specific gravity of 2.56-2.58.

Identified August 3, 2026More mineral →

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Physical properties

Formation & geological history

Formed within igneous rocks such as pegmatites and granites, as well as in metamorphic rocks, through the cooling and exsolution of alternating microscopic layers of orthoclase and albite.

Uses & applications

Widely used in jewelry such as rings, earrings, and pendants; also collected by mineral enthusiasts.

Geological facts

Moonstone gets its shimmering optical phenomenon, known as adularescence, from light scattering between microscopic layers of different feldspar minerals. It has been used in jewelry for centuries, particularly popular during the Art Nouveau period.

Field identification & locations

Identified primarily by its characteristic adularescence (schiller effect) and cleavage. Commonly sourced from Sri Lanka, India, Madagascar, Myanmar, and the United States.

Other mineral specimens

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Sandstone (with potential mineral staining/concretions)

Arenite (SiO2 based)

sedimentary

Soil with Mineral Detritus and Quartz Fragments

Regolith / Silicate Mineral Aggregate

sedimentary

Limonite / Goethite (Iron Ore Mineral nodule)

FeO(OH)·nH2O / FeO(OH)

mineral

Septarian Pebble

Septarian nodule / Concretion

sedimentary

Schist

Metamorphic

Potassium Feldspar (Orthoclase)

Orthoclase (KAlSi3O8)

mineral