cordierite

 
Pronunciation: /ˈkɔːdɪərʌɪt/

noun

[mass noun]
  • a dark blue mineral occurring chiefly in metamorphic rocks. It consists of an aluminosilicate of magnesium and iron, and also occurs as a dichroic gem variety.

Origin:

early 19th century: named after Pierre L. A. Cordier (1777–1861), French geologist, + -ite1