Algodonite Locality: Keweenaw County , Michigan , USA ( Locality at mindat.org ) Size: 8.4 x 5.3 x 5.3 cm. A brassy, nearly solid specimen of algodonite, a rare copper arsenide, from the Keweenaw Peninsula of Michigan. Undoubtedly an old piece. Ex Dr. Gary Hansen Collection. HEAVY at 474 grams or just over 1 pound! — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Algodonite
Algodonite is a copper arsenide mineral with formula: Cu6As. It is a gray white metallic mineral crystallizing in the hexagonal system. It has a Mohs hardness of 4 and a specific gravity of 8.38 – 8.72. It was first described in 1857 from the Algodones silver mine, Coquimbo, Chile.
Intro adapted from Wikipedia (CC BY-SA).
Algodonite is an IMA-recognized mineral species in the sulfide class, with the chemical formula Cu₁₋ₓAsₓ (x ≈ 0.15).
It crystallizes in the hexagonal crystal system (space group P6_3/mmc).
Key properties: Mohs hardness 4; specific gravity 8.38; Bright metallic. Anisotropism: Weak. R1 –R2: (400) 51.5–49.3, (420) 52.3–50.5, (440) 52.8–52.4, (460) 53.4–54.6 luster.
IMA symbol Ago, grandfathered status — known before the IMA’s founding, named in 1857.
Uncommon in hydrothermal deposits, intimately in association with other copper arsenides.
It is found associated with Copper (typically arsenian), silver, domeykite, koutekite.
The name refers to the Algodones mine, Chile.