Emily Dickinson Lexicon

FELD'SPAR, or FEL'SPAR, n. [or FELD'SPATH, or FEL'SPATH. G. feld, field, and spar. It is written by some authors felspar, which is rockspar, or fel is a contraction of field. Spath in German signifies spar.]

A mineral widely distributed and usually of a foliated structure. When in crystals or crystaline 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 silicious, the glassy, the ice-spar, the opalescent, aventurine feldspur, petuntze, the granular, and the compact. Cleaveland.