Mineral - Atacamite
Atacamite
Chemical Properties
Mineral Class
Halides
Toxicity
low
Formula
Cu₂Cl(OH)₃
Unit Cell
a=6.03 b=9.12 c=6.87 Z=4
Physical Properties
Hardness
3 - 3.5
Streak
green
Density
Heavy (3,5-6)
Cleavage
Perfect after {010}, indistinct after {101}
Fracture
conchoidal
Tenacity
Brittle
Optical Properties
Color
greengreen black
Birefringence
0.049
Luster
Vitreous,
Adamantine
Transparency
translucent,
transparent
Pleochroism
X: Hellgrün
Y: Gelb-Grün
Z: Dunkelgrün
Geomineralogical Properties
Crystal System
orthorhombic
Point Group
orthorhombic-dipyramidal - 2/m 2/m 2/m
Space Group
Pnma (62)
Habit
leafy, fibrous, spherical, acicular, prismatic, radial, tabular
Formation
In the oxidation zone of supergene copper deposits
Through resublimation from volcanic gases (fumaroles)
Paragenesis
Twinning
Rare Penetration twins in the direction of [544]
Rarity
Rather rare
Synonyms
Atacamite
Composition
Elements
Mass
CuO
14.53
CoO
55.33
CaO
0.21
Cl
0.23
H₂O
16.22
13.15
Chile (Larsen & Tripp 1972)
Groups and Members
Atacamite-Group
Name and first record : Named after the type locality in the Atacama Desert in Chile. First described in 1803.
Chemistry :
Synonyms : Alacamite, Arsenillo, Atakamite, Halochalcite, Marcylite, Remolinite
Varieties :
Abbreviation : Ata
literature
Larsen, AL, Tripp, RB (1972) New X-ray data on natural atacamite. US Geol. Surv. Prof. Paper 800B : 119-120.