feldspathoid

(redirected from feldspathoidal)
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Related to feldspathoidal: alkali feldspar, sanidine

feld·spath·oid

 (fĕld-spăth′oid′, fĕl-)
n.
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.]

feldspathoid

(ˈfɛldspəˌθɔɪd) or

felspathoid

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

feld•spath•oid

(ˈfɛld spæˌθɔɪd, ˈfɛl-)

adj.
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.
n.
2. a mineral of this group, as nepheline or leucite.
[1895–1900; < German Feldspat(h) (see feldspar) + -oid]
References in periodicals archive ?
Alkali-rich rocks and feldspathoidal rocks are tare (feldspathoids and quartz are mutually exclusive) and plagioclase typically dominates over alkalifeldspar.