Luster is vitreous to sub-adamantine or greasy. Crystals are transparent to translucent. Crystal Habits include pseudo-octahedral crystals that are actually orthorhombic dipyramids. Also tabular crystals and fibrous and crusty coatings. Cleavage is very poor in a few directions.
Fracture is conchoidal.
Hardness is 3.5 - 4. Streak is white. Soluble in hydrochloric acid. Associated Minerals are arsenopyrite , limonite , adamite , olivenite , arseniosiderite and other oxidation zone minerals. Best Field Indicators are color, luster, non-fluorescent, associations and crystal habits.