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Gemstone Crystal System Density Hardness Refractive index Treatments
Feldspar monoclinic 2.56 6.0-6.5 1.518-1.526 none



The following is a table to help clarify the feldspars with gemological importance:
Name Chemistry Description
Pladgioclase Sodium Calcium Aluminum Silicate Labradorite (play of color); Spectrolite (play of color)
Microcline Potassium Aluminum Silicate Amazonite (Bright pastel greenish blue)
Oligoclase Sodium Aluminum Silicate Sunstone (gold spangles from included platelets of hematite)
Orthoclase Potassium Aluminum Silicate Moonstone (transparent with floating blue)


Feldspar is a group of minerals that are very important in rock formation, accounting for over half the earth's crust! There are a number of varieties that are used in jewelry. The most important are moonstone, and labradorite, both known for their phenomenal iridescence and adularescence.

Amazonite was used by the ancient Egyptians for the carving of deities. The stone was considered a catalyst between the living and the gods. Moonstone was thought to drive away sleeplessness.

amazonite with smoky quartz

Above is a classic association of amazonite with smoky quartz.