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Aluminosilicates of sodium, potassium, or calcium that are similar in composition to feldspars but contain less silica than the corresponding feldspar.



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.

References in periodicals archive ?
As K sources, the feldspathoids nepheline and balliranoite and biotite mica could be considered, with high weathering rates of the latter according to the Goldich dissolution series (Goldich, 1938).
The feldspathoids nepheline and balliranoite, zeolite analcime and feldspar sanidine, which include Na in their chemical composition, may be the minerals that release Na, making it available in solution.
A linear K release over the period of 1 year was observed for the feldspathoid nepheline at pH 5, with reduced K release at pH 7.
This behaviour is related with the presence of feldspathoids in the pelletized material.
Back-scattered electron and secondary electron images of altered feldspathoids confirmed zones with different ratios of intimately intergrown thomsonite and gonnardite resembling primary feldspathoid zoning and shaping.
Both the studied rock samples are porphyritic, with a small amount of phenocrysts formed by ferrifassaite passing to sodic ferrifassaite with kaersutite rims, oligoclase-andesine, and minor zeolitized feldspathoid. Andesine to oligoclase ([An.sub.27-30]) predominate over sodic sanidine and scarce clinopyroxene and titanomagnetite in the matrix of fresh trachyandesite facies.
A small amount of pseudomorphs after feldspathoid (sodalite?) is also present.
The microphenocrysts of totally zeolitized feldspathoid are clouded, reminding primary sodalite crystals only in their sub-rounded morphology (see Plate I, 3).