feldspar (n.) Look up feldspar at Dictionary.com
type of mineral common in crystalline rocks, 1785, earlier feldspath (1757), from older German Feldspath (Modern German Feldspat), from Feld "field" (see field (n.)) + spath "spar, non-metallic mineral, gypsum" (see spar (n.2)); spelling influenced by English spar "mineral." Related: Feldspathic.