oligoclase

noun

ol·​i·​go·​clase ˈä-li-gō-ˌklās 

ˈō-,

-ˌklāz;

ə-ˈli-gə- 

: a mineral of the plagioclase series

Word History

Etymology

German Oligoklas, from olig- olig- + Greek klasis breaking, from klan to break — more at clast

First Known Use

1832, in the meaning defined above