Main Entry: an·or·tho·site

Pronunciation: \ə-ˈnȯr-thə-ˌsīt\

Function: noun

Etymology: French anorthose, a feldspar, from a- + Greek orthos — more at orth-

Date: 1863

: a granular plutonic igneous rock composed almost exclusively of a soda-lime feldspar (as labradorite)

— an·or·tho·si·tic \ə-ˌnȯr-thə-ˈsi-tik\ adjective