FEL'SPAR, FEL'SPATH, noun A mineral widely distributed and usually of a foliated structure. When in crystals or crystalline masses, it is very susceptible of mechanical division at natural joints. its hardness is a little inferior to that of quartz. There are several varieties, as common feldspar, the adularia, the siliceous, the glassy, the ice-spar, the opalescent, aventurine feldspar, petuntze, the granular, and the compact.
Source: Webster's 1828 American Dictionary ↗ · public-domain · returned verbatim, no AI