The Collaborative International Dictionary
Ottrelite
Ottrelite \Ot"trel*ite\, n. [From Ottrez, on the borders of Luxembourg.] (Min.) A micaceous mineral occurring in small scales. It is characteristic of certain crystalline schists.
Wiktionary
ottrelite
n. (context mineralogy English) A form of the mineral chloritoid.
Wikipedia
Ottrelite
Ottrelite is a form of chloritoid. Its empirical formula is ( Mn, Fe, Mg) Al Si O(O H).