What is "pearceite"

n. (context mineralogy English) A trigonal-hexagonal scalenohedral black mineral containing antimony, arsenic, copper, silver, and sulfur.

Pearceite is one of the four so-called "ruby silvers", pearceite Cu(Ag,Cu)AgAsS, pyrargyrite AgSbS, proustite AgAsS and miargyrite AgSbS. It was discovered in 1896 and named after Dr Richard Pearce (1837–1927), a Cornish–American chemist and metallurgist from Denver, Colorado.