Mineral - Spinel
Spinel
Chemical Properties
Mineral Class
Oxides and Hydrxides
Toxicity
none
Formula
MgAl₂O₄
Unit Cell
a=8.09 Z=8
Physical Properties
Hardness
8
Streak
white
Density
Heavy (3,5-6)
Cleavage
Indistinct after {111}
Fracture
splintery,
uneven
Tenacity
Brittle
Optical Properties
Color
blackbrownredorangeyellowgreenbluevioletcolorless
Birefringence
Luster
Vitreous
Transparency
translucent,
transparent,
opaque
Pleochroism
Geomineralogical Properties
Crystal System
isometric
Point Group
hexoctahedral - 4/m 3 2/m
Space Group
Fd 3 m (227)
Habit
dodecahedron, granular, Octahedron, Cube
Formation
(1) Magmatic, as an accessory mineral in mafic to ultramafic rocks, as well as through fractional crystallization from aluminum-rich melts.
(2) Metamorphic, formed by contact or regional metamorphism in Al-rich sediments (metapelites) or impure limestones (skarns) under high temperatures.
Paragenesis
Twinning
Contact twins after {111} -Spinel law
Rarity
Common
Synonyms
Spinel
Composition
Elements
Mass
SiO₂
0.02
TiO₂
0.05
Al₂O₃
70.08
FeO
0.33
ZnO
0.33
MgO
28.77
Vietnam (Palache et al. 1952)
Groups and Members
Spinel-Supergroup
Oxyspinel-Group
Spinel-Subgroup