The
Feldspathoid minerals are not a typical mineral group
that are related by structure and chemistry. Their relationship
to each other is primarily due to their relationship
to the Feldspar Group of
minerals. Minerals with chemistries that are close to
those of the alkalai Feldspars but are poor in silica
(SiO2)
content are called Feldspathoids. Feldspathoids are
low silica igneous minerals. As an example, Leucite
is found in silica poor rocks containing other silica
poor minerals and no Quartz.
If Quartz were present when the magma was cooling and
crystalizing,
it would react with any Feldspathoids and form Feldspar.
The following are some of the more common Feldspathoid minerals:
- Afghanite
(Hydrated
Sodium Calcium Potassium Aluminum Silicate Carbonate)
- Cancrinite (Sodium Calcium Aluminum Silicate Carbonate)
- Danalite
(Iron Beryllium Silicate Sulfide)
- Helvine
(Helvite)
(Manganese Beryllium Silicate Sulfide)
- Leucite
(Potasium
Aluminum Silicate)
- Nepheline
(Sodium
Potasium Aluminum Silicate)
- Sodalite Group:
- Haüyne
(Sodium Calcium
Aluminum Silicate Sulfate)
- Lazurite
(Sodium
Calcium Aluminum Silicate Sulfate Sulfide Chloride)
- Nosean (Sodium
Aluminum Silicate Sulfate)
- Sodalite
(Sodium
Aluminum Silicate Chloride)
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