Overview
About Moonstone
Moonstone is a variety of the feldspar-group mineral orthoclase. During formation, orthoclase and albite separate into alternating layers. When light falls between these thin layers it is scattered producing the phenomenon called adularescence. Adularescence is the light that appears to billow across a gem. Other feldspar minerals can also show adularescence including labradorite and sanidine.
Birthstones & Anniversaries
Moonstone is a birthstone for June, along with pearl and alexandrite.
Adularescence
Moonstone’s unearthly glow is caused by light scattering between microscopic layers of feldspar.
60%
The minerals in the feldspar family make up more than half of the Earth’s rocky crust.
0.5 Microns
Feldspar layers that create moonstone’s sheen are similar to the size of a wavelength of light.
Facts
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Mineral:
Feldspar
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Chemistry:
KAlSi3O8
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Color:
Colorless to White, Gray, Green, Peach, Brown
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Refractive index:
1.518 to 1.526
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Birefringence:
0.05 to 0.008
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Specific gravity:
2.58
- Mohs Hardness: 6.0 to 6.5
Treatments
There are a number of processes used to alter the color, apparent clarity, or improve the durability of gems.
Learn MoreSynthetics
Some gemstones have synthetic counterparts that have essentially the same chemical, physical, and optical properties, but are grown by man in a laboratory.
Learn MoreImitations
Any gem can be imitated—sometimes by manmade materials or by natural materials chosen by man to impersonate a particular gem.
Learn More
Why We Love This Gemstone
Rarity
Rare in top qualities, this ethereal gem derives from one of the earth's most common minerals.
Adularescence
Stacked layers of orthoclase and albite diffract light, creating moonstone’s adularescence.
Another Phenomena
Besides adularescence, moonstone sometimes also shows a cat’s-eye effect.
Quality Factors
An assessment of the following characteristics determines moonstone’s value.
Color
The finest moonstone is a gem of glassy purity with a mobile, electric blue shimmer.
Clarity
Characteristic inclusions include tiny tension cracks called centipedes.
Cut
As it displays moonstone’s phenomena to best advantage, cabochon is the common cut.
Carat Weight
Moonstone comes in a wide range of sizes and carat weights.
Moonstone Quality Factors: The Comprehensive Guide
Research
Explore sources, gemological research, and the role of gems in history.
New High-Quality Rainbow Moonstone from Madagascar
Jennifer Stone-Sundberg , May 3, 2024 Read ArticleA Tropical Paradise of Ocean-Inspired Jewelry and Gemstones
Sharon Bohannon , Aug 9, 2019 Read Article
Metalwork Takes a Bow: Techniques that Enhance Gemstone Jewelry
Sharon Bohannon , Nov 9, 2018 Read ArticleRecommended Reading
Feldspar Minerals: Crystal Structures, Physical, Chemical and Microtextural Properties
Joseph V. Smith and William L. Brown
