feld·spath·oid 
(fĕld-spăthoid′, fĕl-)
(fĕld-spăthoid′, 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.]