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.

References in periodicals archive ?
Whereas phosphatic rocks are feedstock for both conventional and unconventional phosphate fertilizers, potassium silicates, such as feldspars, biotite, phlogopite, and muscovite, and rocks with feldspathoids, such as leucite, nepheline and clayrich sediments, especially illite, are the basis for alternative potassium fertilization (Straaten, 2010).
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 small amount of pseudomorphs after feldspathoid (sodalite?
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.
The microphenocrysts of totally zeolitized feldspathoid are clouded, reminding primary sodalite crystals only in their sub-rounded morphology (see Plate I, 3).
1991) Pitiglianoite, a new feldspathoid from southern Tuscany, Italy: chemical composition and crystal structure.
This behaviour is related with the presence of feldspathoids in the pelletized material.
4B: Framework silicates; silica minerals, feldspathoids and the zeolites, 2d ed.
To the researchers' surprise, over time the contaminants in the experimental set-ups were bound by newly formed clays, forming unusual minerals called zeolites and feldspathoids.