Outstanding specimen of black elongated arsenolamprite crystals from a German locality. Arsenolamprite is a native element dimorph of native arsenic, but much rarer. From: Mackenheim Quarry, Odenwald, Hesse, Germany. — Photo: David Hospital · CC BY-SA 4.0
Arsenolamprite
Arsenolamprite is an IMA-recognized mineral species in the native element class, with the chemical formula As.
It crystallizes in the orthorhombic crystal system (space group Bmab). It is a member of the Arsenolamprite structural group.
Key properties: Mohs hardness 2; specific gravity 5.3–5.5; Black streak; Metallic, brilliant. Anisotropism: Weak. R1 –R2: (400) —, (420) 42.8–56.8, (440) 43.6–55.4, (460) 44.3–54.0 luster.
IMA symbol Asl, grandfathered status — known before the IMA’s founding, named in 1886.
Occurs as plates and veinlets in carbonate rocks (Černý Důl mine, Czech Republic); in calcite veins (Mackenheim, Germany).
It is found associated with Arsenic, bismuth, silver, sternbergite, emplectite, safflorite, löllingite, pyrite, galena, orpiment, realgar, calcite.
The name comes from its composition and the Greek for brilliant, in allusion to its reflectance.