mineral

Moonstone (Blue Flash)

Potassium Aluminum Silicate (KAlSi3O8), a variety of Orthoclase Feldspar

Hardness: 6.0–6.5 (Mohs); Color: White to translucent with blue adularescence; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect in two directions; Specific gravity: 2.56–2.59

Hardness: 6
Color: White to translucent with blue adularescence
Luster: Vitreous to pearly

Identified March 28, 2026More mineral →

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Physical properties

Formation & geological history

Formed in igneous and metamorphic rocks through the cooling of magma, where orthoclase and albite separate into alternating layers. The blue sheen (adularescence) is caused by light scattering between these microscopic layers.

Uses & applications

Primarily used in jewelry (cabochon cut), beadwork, and as a popular specimen for gemstone collectors and holistic practices.

Geological facts

Ancient Romans believed moonstone was formed from frozen rays of the moon. It is the birthstone for June and is famous for its 'cat’s eye' or 'star' effects in rare high-quality specimens.

Field identification & locations

Identify by looking for the blue 'shimmer' that moves across the surface as the stone is turned. It is commonly found in Sri Lanka, India, Madagascar, and Myanmar. Collectors should look for high transparency and a strong, centered blue flash.

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