MOONSTONE

Photo courtesy of Scott Papper, GIA GG, AJP, CM (NAJA), Global Gemology & Appraisals

Variety:  Moonstone
Species:  Orthoclase
Group:  Feldspar
​​Mohs Hardness:  6 to 6.5 out of 10
Color:  Semi-translucent to opaque.  Generally colorless to white, but can be orange, yellow or brown.  With adularescence.
RI:  1.518 to 1.526 (+0.010)
Birefringence:  0.005 to 0.008
SR/DR/AGG:  DR or AGG (depending on transparency)
Clarity Type:  Type II
Optic Character:  Biaxial negative (may show repeated twinning under crossed polarized filters)
Spectrum:  Not diagnostic
Fluorescence:  Inert to blue under LW.  Orange under SW.  Might fluoresce weak pink to red under LW & SW.
SG:  2.58 (+/-0.03)
Routine Treatments:  None

Moonstone Facts

Moonstone is a variety of the feldspar-group mineral, orthoclase.​

Moonstone possesses a phenomena known as "adularescence".

Adularescence appears as a light that billows across the gem, caused by the scattering of light between microscopic layers.

The minerals in the feldspar family make up roughly 60% of the earth's crust.  Other varieties of feldspar include orthoclase, labradorite, sunstone & amazonite.

​Moonstone is a June birthstone.
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