The Collaborative International Dictionary
Sternbergite
Sternbergite \Stern"berg*ite\, n. [So named after Count Kaspar Sternberg of Prague.] (Min.) A sulphide of silver and iron, occurring in soft flexible lamin[ae] varying in color from brown to black.
Wiktionary
sternbergite
n. (context mineralogy English) An orthorhombic-dipyramidal light brown mineral containing iron, silver, and sulfur.