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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 ?
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).
A small amount of pseudomorphs after feldspathoid (sodalite?) is also present.
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.
(1994) Quadridavyne, [[(Na,K).sub.6][Cl.sub.2]][[Ca.sub.2][Cl.sub.2]][[Si.sub.6][Al.su b.6][O.sub.24]], a new feldspathoid mineral from Vesuvius area.
Similar to gabbro and anorthosite, norite is very rich in plagioclase compared to K-feldspar, feldspathoids, and quartz [11, 12].
There are 12 types classified in nature along with similar minerals called feldspathoids such as nepheline syenite.
By other hand, the feldspathoids presented in the pellets do not have capacity to adsorb EGME.
Alkali-rich rocks and feldspathoidal rocks are tare (feldspathoids and quartz are mutually exclusive) and plagioclase typically dominates over alkalifeldspar.
Likewise, altered feldspathoids in the nepheline syenites in the Bancroft, Ontario area (formerly called "hydronephelite" or "giesekite") are mixtures of natrolite and muscovite, [+ or -] analcime and other minor constituents.
Rock-forming minerals; v.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. The mineral particles, about 1,000 times smaller than a grain of sand, do not dissolve easily and therefore keep the contaminants trapped in the soil.