Stone of the Week - Moonstone

Tuesday, January 29, 2008
Moonstone is a type of feldspar called orthoclase; feldspars are a group of minerals composed of aluminum silicates, and are the most common rock forming mineral on Earth. Moonstone, as well as a number of other minerals in this group, stands out for it’s ability to diffract reflected light creating a sheen (technical term is Schiller or Adularescence). In the case of Moonstone, it is often a silver to blue color sheen that is reflected.

Schiller or Adularescence is what gives Moonstone its 'glow' or 'sheen', which is usually silver or blue.

Moonstone comes in several colors, the more common being white, gray, and peach. White Moonstone, with an especially strong bluish sheen, is often called Rainbow Moonstone, and is actually not a moonstone but another feldspar mineral called Labradorite; it is very popular to use in jewelry. The most valuable is the blue Moonstones from Sri Lanka, particularly as there are fewer being found thus driving up prices for this most beautiful of stones.

Moonstone comes in a variety of color, though the more common ones are gray, peach, and white.

Moonstone is a historically important gem, valued by royalty and commoners alike. It was very popular during the Art Nouveau, and currently is the preferred birthstone for June in several European countries. In several cultures, Moonstone is considered to be magical and have special properties. Some in India regard this stone as a ‘dream stone’, bringing good visions at night, while in some Arabic communities, women will sew these into their clothing as it is a symbol of fertility.

Rainbow Moonstone has a lovely blue sheen that is very desirable by jewelry artisans, although the name is a misnomer as its actually a type of Labradorite instead of Moonstone.

If there's a stone you would like to know more about - drop me a line! Have a mystery stone? Feel free to post a comment about it, including a link to a picture, and it could be featured on this blog!

Moonstone Facts:
Chemical composition: KAlSi3O8
Crystal System: Monoclinic
Color: Most commonly white, peach, or gray; also blue, pink, green, and brown
Habit: Prismatic, Tabular
Fracture: Irregular/Uneven, Conchoidal
Cleavage: Perfect
Luster: Vitreous
Hardness: 6
Specific Gravity: ~2.55
Streak: White
Occurrence: Worldwide

A Guide to Rocks and Fossils by B. Busbey III, R. R. Coenraads, P. Willis, and D. Roots. Published 2002 by Fog City Press. ISBN: 1877019518 – Moonstone.

Mindat – Orthoclase.

Wikipedia – Moonstone.


mimi said...

I purchased what I think is a moonstone ring. The stone is cabochon cut,is crystal clear with tiny inclusions and forms a white star(asterism?) in bright light.Can moonstones do this? The star is usually 4 point but sometimes 6 point.