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Gemology Online: Feldspar

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

feldspar

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.