Crystal Habits are limited to mostly massive and granular components of massive hydrothermal sulfide rocks and gabbros, but a few localities have produced good pyramidal or tabular crystals. Columnar and reniform habits are also seen. Rare fourling twins are also seen. Dark brown to black. Upon heating a garlic odor maybe observed due to the arsenic content.
Crystals tend to be striated.
Associated Minerals include arsenopyrite , barite , silver , annabergite , cobaltite , pyrrhotite , pentlandite , chalcopyrite , breithauptite and maucherite . Best Field Indicators are color, density, associations, streak, hardness and odor when heated.