pyrargyrite

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A deep red to black silver ore with composition Ag₃SbS₃.

Century Dictionary and Cyclopedia

1. n. An important ore of silver, consisting of the sulphid of silver and antimony. It occurs in crystals belonging to the rhombohedral system, often highly complex, and also in massive forms. When transparent it has a deep ruby-red color by transmitted light, though on the surface it is nearly black with a metallic adamantine luster; the streak has a cochineal-red color. Also called ruby silver, or, in distinction from proustite, dark-red silver ore. The common Spanish name in Mexico and South America is rosicler oscuro, or sometimes petlanque. See proustite.

Wiktionary

1. n. Ruby silver; dark red silver ore. It is a sulphide of antimony and silver, Ag3SbS3, occurring in rhombohedral crystals or massive, and is of a dark red or black color with a metallic adamantine luster; it is an important silver ore

GNU Webster's 1913

1. n. Ruby silver; dark red silver ore. It is a sulphide of antimony and silver, occurring in rhombohedral crystals or massive, and is of a dark red or black color with a metallic adamantine luster.