Mineral - Amesite
Amesite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Mg₂Al(AlSiO₅)(OH)₄
Unit Cell
a=5.31 b=9.20 c=14.07 α=91° β=91° γ=89° Z=4
Physical Properties
Hardness
2.5 - 3
Streak
whitegreengreen white
Density
Normal (2-3,5)
Cleavage
Perfect after {001}
Fracture
Tenacity
Brittle
Optical Properties
Color
whitegreenpink
Birefringence
0.019
Luster
Vitreous,
Greasy
Transparency
transparent
Pleochroism
Geomineralogical Properties
Crystal System
triclinic
Point Group
triclinic-pedial - 1
Space Group
P1 (1)
Habit
prismatic, columnar, star-shaped, tabular
Formation
Through metamorphism of Mg- and Al-rich rocks
Paragenesis
Twinning
Penetration twins, rotation twins, polysynthetic twins (and combinations)
Rarity
Rather rare
Synonyms
Amesite
Composition
Elements
Mass
SiO₂
20.95
Al₂O₃
35.21
FeO
8.28
MnO
0.01
MgO
22.88
CaO
0.58
H₂O
13.02
Massachusetts (Dana 1892)
Groups and Members
Kaolinite-Serpentine-Group
Serpentine-Subgroup
Name and first discovery : Named in 1876 by Charles Upham Shepard in honor of the wealthy American mineral collector James Tyler Ames (1810-1883), who owned the type locality, the Chester Emery Mines.
Chemistry : Several polytypes are known: 2H1, 2H2, 6R and others.
Synonyms : amenite, amensite, amesine
Varieties :
Abbreviation : Ame
Twins in amesite, which are formed by the combination of three triclinic rhombohedra, which then overlap in a stacked manner.
literature
Dana, J. D., & Dana, E. S. (1892). The system of mineralogy of James Dwight Dana, 1837-1868: descriptive mineralogy . J. Wiley & sons.