Realgar
AsS
Chemical name
Realgar
Mineral name
Realgar
Chemical formula
AsS
Crystal system
monoclinic
Crystal Class
Prismatic (2/m)
Space Group
P21/n (no. 14)
Unit cell
a [Å]:9.325(3)
b [Å]:13.571(5)
c [Å]:6.587(3)
Twinning
Contact twins on {100}
Mohs hardness
1,5-2
Cleavage
Good on {010}; less so on {101}, {100}, {120}, and {110}
Fracture / Tenacity
Sectile, slightly brittle
Streak
Reddish brown
Transparency
Transparent
Optical character
Biaxial (-)
Refractive Index
nα = 2.538 nβ = 2.684 nΥ = 2.704