Moonstone
General
Category	orthoclase feldspar
Chemical formula	KAlSi3O8
Identification
Color	Can be numerous colors, including grey, white, pink, green and brown, but the most valuable are deep blue.
Crystal system	Monoclinic
Mohs Scale hardness	6 - 6.5
Luster	vitreous
Refractive index	1.52 - 1.53 to 1.53 - 1.54
Optical Properties	Biaxial Negative
Dispersion	0.008
Specific gravity	2.55 - 2.58

Moonstone is typically a potassium aluminium silicate, with the chemical formula KAlSi₃O₈.

The most common moonstone is of the mineral adularia. The plagioclase feldspar oligoclase also produces moonstone specimens. Its name is derived from a visual effect, or sheen, caused by light reflecting internally in the moonstone from layer inclusion of different feldspars.

Deposits of moonstone are found in many countries and places: it is found in European Alps, Brazil, India, Mexico, Myanmar, Madagascar, Sri Lanka, the USA; specifically Pennsylvania and Virginia and Tanzania. However, it is Sri Lanka that produces the highest quality moonstones.

Wikimedia Commons has media related to:

Moonstone

This article about a specific mineral or mineraloid is a stub. You can help Wikipedia by expanding it.