Feldspar What is it? What does it do?

FELDSPAR

This the name given to a group of minerals that are made up of potassium and aluminum silicates (orthoclase), sodium and aluminum (albite), or calcium and aluminum (anorthite). This is a mouthfull, I know. The word comes from the German "feldt spat", meaning "field spar", "spar" meaning common clevable material - the material dredged up on farm lands during plowing. Most of them are not affected by acid (exception the Calcium rich plagioclase - Anorthite). Orthoclase got is name from the Greek phrase meaning "straight fracture", Microcline from a Greek phrase meaning "small incline", and Plagioclase from the Greek phrase meaning "oblique fracture".

Here are some pictures that might help you see what we are talking about.

Feldspar is used in the making of glass, as glaze for pottery, and as an abrasive in scouring powder your mother uses to clean the bathtub.



Here are some gem stones associated with feldspar:

Orthoclase - usually light colored white, pink, yellow, or cream, and not transparent. The gem variety is clear to pale yellow, and some called "noble orthoclase" Microcline - white, pink, pale yellow, or sometimes green-blue, and not transparent. The green-blue variety is called "amazonite" Plagioclase - gray to grayish-white is common, but may also be white, pink or pale yellow. More semi-opaque than the other feldspars on average, and contains striations on some crystal faces or cleavage surfaces.