The Collaborative International Dictionary
Perthitic
Perthite \Perth"ite\, n. [So called from Perth, in canada.] (Min.) A kind of feldspar consisting of a laminated intertexture of albite and orthoclase, usually of different colors. -- Per*thit"ic, a.
Wiktionary
perthitic
a. (context geology English) Of, pertaining to, or resembling perthite