Mineral - Realgar
Realgar
Chemical Properties
Mineral Class
Sulfides and sulfosalts
Toxicity
middle
Formula
As₄S₄
Unit Cell
a=9.33 b=13.57 c=6.59 β=106° Z=16
Physical Properties
Hardness
1.5 - 2
Streak
redorangeorange red
Density
Heavy (3,5-6)
Cleavage
Distinct after {010}, indistinct after {100}, { 1 01}, {120} and {110}
Fracture
Tenacity
Elastic-flexible
Optical Properties
Color
redorange
Birefringence
0.166
Luster
Greasy,
Adamantine
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
P2 1 /c (14)
Habit
blocky, coarse, prismatic, Rhombohedron, tabular
Formation
(1) Hydrothermal formation in veins at low temperatures
(2) Volcanic formation through direct sublimation from volcanic gases (fumaroles)
(3) Secondary formation as a product of the transformation of other arsenic minerals in the oxidation zone of arsenic ore deposits
Paragenesis
Twinning
Contact twins after {100}
Rarity
Rather rare
Synonyms
Realgar
Composition
Elements
Mass
As
69.54
S
30.29
Switzerland (Palache et al. 1952)