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Moonstone Gemstone Information

Moonstone is a variety of feldspar that displays a shimmering light effect or sheen that resembles moonlight. The effect is called adularescence or schiller and is caused by the interference of light through lamellar layers within the stone. Moonstone occurs in various colours as described below, those with a bluish colour are the most sought after and are therefore more expensive.

Moonstones can display chatoyancy, a 'cat's eye effect' made possible when sufficient amounts of parallel needle-like inclusions are present throughout the stone.

Source locations for Moonstone include: Australia, Brazil, India, Madagascar, Myanmar, Sri Lanka and the USA.

Physical Properties

Stone type:
Moonstone is a variety of feldspar, from the Alkali Feldspar Sub-group.
Crystal System:
Monoclinic.
Chemical Composition:
Potassium aluminium silicate, K(AlSi3O8).
Colour:
Colourless, white, silvery-white, bluish-white, also occurs in pink yellow, green, brown and grey to dark grey.
Lustre:
Vitreous.
Pleochroism:
Absent.
Dispersion:
Low.
Hardness:
6 to 6½ on the Mohs' scale of hardness.
Toughness:
Poor: Moonstone is a soft stone with perfect cleavage. It is susceptible to thermal shock 'sudden temperature change' that may fracture the stone.
Cleavage:
Perfect.
Density in gm/cc:
2.56 to 2.59
Double refraction:
Yes.
Refractive index:
1.518 to 1.526

Common Treatments

Moonstone is not normally treated.


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