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Feldspar Group

    

 


The Feldspar group of minerals includes these gem types: Albite, Amazonite, Andesine, Anorthite, Bytownite, Hyalophane, Labradorite, Moonstone, Oligoclase, Orthoclase, Sanidine and Sunstone.

Ther are nearly 20 members recognized in the Feldspar group, but only nine are well known and common. Those few, however, make up the greatest percentage of minerals found in the Earth's crust.

The following are some of the more common Feldspar minerals:

The Plagioclase Feldspars:

  • Albite (Sodium aluminum silicate)
  • Oligoclase  (Sodium calcium aluminum silicate)
  • Andesine  (Sodium calcium aluminum silicate)
  • Labradorite  (Calcium sodium aluminum silicate)
  • Bytownite  (Calcium sodium aluminum silicate)
  • Anorthite  (Calcium aluminum silicate)

The Potassium-Feldspars or alkali Feldspars:

The Feldspars are a group of minerals that have similar characteristics due to a similar structure. All Feldspars have low symmetry, being only monoclinic. They tend to twin easily, occassionally producing parallel layers of twinned crystals. They are relatively hard at around 6, and have an average density of 2.55 to 2.76. They have a rather dull to rarely vitreous luster. Crystals tend to be blocky. Some Feldspars may be triboluminescent. They have two directions of cleavage at nearly right angles. As a matter of fact, the name Feldspar comes from the Greek phrase meaning oblique fracture, because of the angle between the two prominent cleavages.

 

Albite

 

Andesine

 

Anorthite

 

Bytownite
Albite

 

Andesine

 

Anorthite

 

Bytownite

 

 

 

 

 

 

 

Hyalophane

 

Labradorite

 

Microcline (variety Amazonite)

 

Moonstone
Hyalophane

 

Labradorite

 

Microcline

 

Moonstone

 

 

 

 

 

 

 

Oligoclase

 

Orthoclase

 

Sanidine

 

Oregon Sunstone
Oligoclase

 

Orthoclase

 

Sanadine

 

Sunstone

 

 

 

 

 

 

 

Valencianite

 

 

 

 

 

 

Valencianite

 

 

 

 

 

 

 

 

 

 

 

 

 

 


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