Mineral - Almandine
Almandine
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Fe₃Al₂[SiO₄]₃
Unit Cell
a=11.53 Z=8
Physical Properties
Hardness
7 - 7.5
Streak
white
Density
Heavy (3,5-6)
Cleavage
Good after {110}
Fracture
conchoidal
Tenacity
Brittle
Optical Properties
Color
blackred
Birefringence
Luster
Vitreous
Transparency
translucent,
transparent
Pleochroism
Geomineralogical Properties
Crystal System
isometric
Point Group
hexoctahedral - 4/m 3 2/m
Space Group
Ia 3 d (230)
Habit
Deltoidal icositetrahedron, dodecahedron
Formation
Through Metamorphism, in mica schists and gneisses; Through metasomatism in hornfelses and eclogites; Also igneous in granites
Paragenesis
Twinning
Rarity
Very common
Synonyms
Almandine, Dhanrasite
Composition
Elements
Mass
SiO₂
37.39
TiO₂
0.16
Al₂O₃
20.72
Fe₂O₃
0.83
FeO
36.37
MnO
0.86
MgO
3.85
CaO
0.41
Sweden (Dana 1892)
Groups and Members
Garnet-Supergroup
Garnet-Group
Name and first discovery : Named after the ancient city of Alabanda in Turkey, where almandine was first mined, but never found. Almandine was already known to Pliny the Elder (c. 23–79 AD) under the name alabandicus.
Chemistry : Almandine is the iron-rich end member of the almandine-pyrope series and the almandine-spessartine series.
Synonyms : Greenlandite, Adelaide Ruby, Almandite
Varieties : Dhanrasite, Star Garnet
literature
Dana, J. D., & Dana, E. S. (1892). The system of mineralogy of James Dwight Dana, 1837-1868: descriptive mineralogy . J. Wiley & sons.