Moonstone

Moonstone is the opalescent variety of orthoclase, with a blue or white sheen (or schiller). It is not like the shine of the moon after which it is named. The schiller effect is due to the reflection of light from the internal structure. That is made up of alternating layers of albite and orthoclase feldspar. Thin albite layers produce a white schiller. It is rare to find moonstone of a large size and fine quality.

Moon worshippers have used the stone in jewelry for ages. Moonstone is usually cut as cabochon and cameo. It is common to find a rough crystal with a pitted surface and a frosty glass appearance. Similarly, it also occurs as a waterworn pebble.

Occurrence

The best moonstone occurs in Myanmar (Burma) and Sri Lanka. Other localities include Tanzania, the European Alps, Mexico, the USA, Brazil, Madagascar, and India.

Moonstone Properties

• Specific Gravity: 2.57
• Refractive Index: 1.52-1.53
• Birefringence (DR): 0.005
• Luster: Vitreous
• Crystal Structure: Monoclinic
• Composition: Potassium aluminum silicate
• Hardness: 6

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