Feldspathoid

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feldspathoid

[′fel‚spa‚thȯid]
(geology)
Aluminosilicates of sodium, potassium, or calcium that are similar in composition to feldspars but contain less silica than the corresponding feldspar.

Feldspathoid

 

a group of alkali rock-forming minerals (aluminosilicates) that are not as rich in silica as the feldspars. The structure of the feldspathoids characteristically includes additional anions, such as Cl, CO32–, SO42–, S2–, and sometimes H2O. The feldspathoids replace the feldspars in alkalic rocks and some basic rocks. The major feldspathoid minerals include nepheline, leucite, sodalite, nosean, haiiyne, and cancrinite.