Mineral - Actinolite
Actinolite
Chemical Properties
Mineral Class
Silicates
Toxicity
none
Formula
Ca₂(Mg,Fe)₅[OH|Si₄O₁₁]₂
Unit Cell
a=9.89 b=18.20 c=5.31 β=105° Z=2
Physical Properties
Hardness
5 - 6
Streak
white
Density
Normal (2-3,5)
Cleavage
Good on (110), with intersections of 56°± and 124°±
Fracture
Tenacity
Optical Properties
Color
blackgraygreen
Birefringence
0.023
Luster
Vitreous,
Silky
Transparency
translucent,
transparent,
opaque
Pleochroism
Geomineralogical Properties
Crystal System
monoclinic
Point Group
monoclinic-prismatic - 2/m
Space Group
C2/m (12)
Habit
fibrous, acicular, prismatic, columnar
Formation
Metamorphosim
Paragenesis
Twinning
Contact twins on (100)
Rarity
Very common
Synonyms
Actinolite
Composition
Elements
Mass
SiO₂
55.17
TiO₂
0.17
Al₂O₃
2.69
FeO
11.07
MnO
0.18
MgO
16.21
CaO
12.08
Na₂O
0.82
Wales (Dana 1892)
Groups and Members
Amphibole-Supergroup
Calcium-Amphibole-Group
Actinolite-(Act)-Amphibole-Subgroup
Name and first discovery : Named in 1794 by Richard Kirwan from the Greek "aktina" for ray and "lithos" for stone in reference to the fibrous nature of the original specimens.
Chemistry : Actinolite is an intermediate member of the actinolite-tremolite series within the amphiboles. Actinolite has a Mg/(Mg+Fe2+) ratio of 0.5–0.9, and ferroactinolite has a ratio of less than 0.5.
Synonyms : stibolite, stralite, zillerthite, zillertite, actynolite
Varieties : Emeraldite
literature
Dana, J. D., & Dana, E. S. (1892). The system of mineralogy of James Dwight Dana, 1837-1868: descriptive mineralogy . J. Wiley & sons.