Feldspathoid Gems

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)
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)