Forsterite

( Min.) A silicate of magnesia found at Vesuvius, in orthorhombic crystals of a vitreous lustre, and white, whitish, or greenish color. Sp. gr. 3-213:33. Comp. Silica 42-86, magnesia 57.14. Forswear, (for-zware',) v. a. ( imp . FORSWORE; pp. FORSWORN.) [A.S. forswerian , from for , and swerian , to swear; Ger. verschwören.] To reject or renounce upon oath; to abjure; to deny upon oath. To swear falsely; to perjure one's self. (With reciprocal pronoun.) "Thou shalt not forswear thyself." - Matt. v. 33. -v. n. To swear falsely; to commit perjury. Forswear'er, n. One who rejects on oath; one who is perjured; one who swears a false oath. Forswore', imp . of FORSWEAR, q. v. Forsworn', pp . of FORSWEAR. Renounced on oath; perjured.