chalcophanite

from The Century Dictionary.

• noun A hydrous oxid of manganese and zinc, occurring in druses of minute tabular crystals of a bluish-black color and metallic luster at Stirling Hill in New Jersey. It assumes a bronze color when heated before the blowpipe, whence the name.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun mineralogy A trigonal-rhombohedral mineral containing hydrogen, iron, manganese, oxygen, and zinc.