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 (fĕld-spăth′oid′, fĕl-)
Any of a group of relatively rare minerals that are chemically very similar to feldspars, but have too little silica to qualify as feldspars.

[feldspath (obsolete variant of feldspar, from obsolete German Feldspath, feldspar; see feldspar) + -oid.]


(ˈfɛldspəˌθɔɪd) or


(Geological Science) any of a group of rock-forming minerals, such as leucite and sodalite, that are similar to feldspars but contain less silica


(ˈfɛld spæˌθɔɪd, ˈfɛl-)

1. Also, feld`spath•oi′dal. of or pertaining to a group of minerals similar in chemical composition to certain feldspars except for a lower silica content.
2. a mineral of this group, as nepheline or leucite.
[1895–1900; < German Feldspat(h) (see feldspar) + -oid]
References in periodicals archive ?
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.
Frost and Frost (2008) devised a means of classifying alkaline igneous rocks and comparing their geochemistry with "normal" granitic rocks based a plot of alkalinity index (AI) versus feldspathoid silica saturation index (FSSI) (refer to Fig.
Topaz is a silicate mineral most often found in igneous rocks of felsic (relating to an igneous rock that contains a group of light-colored silicate minerals, including feldspar, feldspathoid, quartz, and muscovite) composition.
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.
In its thin sections, the rock has a hypo-crystalline matrix which is composed of porphyritic texture and is rich in a sprinkled opaque mineral, plagioclase, feldspathoid mineral and obsidian.
It is a partially decomposed granite feldspathoid having a greater diversity of alkaloids causing it to go into a gradual melt with less surface tension than true feldspars.
24]], a new feldspathoid mineral from Vesuvius area.
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.
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.