staurolite

noun

stau·​ro·​lite ˈstȯr-ə-ˌlīt 

: a mineral consisting of a basic silicate of iron and aluminum in prismatic orthorhombic crystals often twinned so as to resemble a cross

staurolitic

ˌstȯr-ə-ˈli-tik 

adjective

Word History

Etymology

French, from Greek stauros cross + French -lite — more at steer

First Known Use

circa 1815, in the meaning defined above