The mineral arsenopyrite
Arsenopyrite – Sulfide mineral – FeAsS – 2.EB.20 – Monoclinic – Prismatic (2/m) – P2₁/c – A = 5.744, b = 5.675 – C = 5.785 [Å]; β = 112.3°; Z = 4 – Steel grey to silver white – Acicular, off-square prismatic, stubby; striated; also compact, granular, columnar – Common on {100} and {001}, contact/penetration twinning on {101} – 110 (distinct) – Subconchoidal to rough – Brittle – 5.5–6 – Metallic – Black – Opaque – 5.9–6.2 – Anisotropism – strong red-violet – Weak, white or bluish tint, faint reddish yellow – Yes – Nitric acid – Garlic odour when struck, greenish tinge when weathered, green staining of wall rocks.
The mineral arsenopyrite
Arsenopyrite crystal from the Yaogangxian Mine, Hunan, China (size: 2.7 x 2.0 x 1.7 cm)