Mineral Information and Data:

Atacamite
Cu2Cl(OH)3 [CNMNC approved formula]

Named after the type locality, in the Atacama Desert of northern Chile.

IMA status : Valid species (Pre-IMA 1801) Grandfathered
CLASSIFICATION 
Dana
(8th edition) :
10.01.01.01  
  (10) Oxyhalides and Hydroxyhalides
  (10.01) where (A)2 (O,OH)3 Xq
  (10.01.01) Atacamite group
  
Nickel-Strunz
(10th edition) :
03.DA.10a
  (03) Halides
  (03.D) Oxyhalides, Hydroxyhalides and Related Double Halides
  (03.DA) With Cu, etc., without Pb
  
Crystal system: Orthorhombic System
Point group (H-M): mmm (or 2/m 2/m 2/m) — dipyramidal
Unit cell: a = 6.030 Å, b = 9.122 Å, c = 6.868 Å
Crystal Habit: Crystals slender prismatic; tabular; often striated; crusts of subparallel crystals; massive, granular
Twinning: On {110} rare, contact or penetration (doublets, trillings), about [544] more common
  
Color: Bright to dark green
Diaphaneity: Transparent to translucent
Luster: Adamantine to vitreous
Hardness (Mohs): 3 to 3.5
Measured Density: 3.75 to 3.78 g/cm3
Cleavage: 2; {010} perfect, {101} fair
Tenacity: Brittle
Fracture: Conchoidal
Streak: Apple-green
  
Polymorphism and Series: Polymorphous with botallackite, clinoatacamite, and paratacamite.
Geologic Setting: An oxidation product of other copper minerals, especially under arid, saline conditions; in fumarolic deposits; a weathering product of sulfides in subsea black smoker deposits; an alteration of bronze and copper objects of antiquity.
Mineral Association: Cuprite, brochantite, linarite, caledonite, malachite, chrysocolla, paratacamite,
botallackite
  
Synonyms/varieties: Paratacamite
Other Properties: Gemstone Unlikely Available. BioMineral.

 

Atacamite
Origin: La Farola mine, Copiapo, Atacama, Chile
Owner: Lou Perloff
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Atacamite
Origin: Mammoth mine, Tiger, Pinal Co., Arizona, U.S.A.
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Atacamite
Origin: Copiapo, Atacama Prov., Chile
Sample size: 7 x 5 x 2 cm
Photo: Tom Loomis

 

Atacamite
(zoom-in of above)

 

Atacamite
Origin: Mammoth mine, Tiger, Pinal Co., Arizona, U.S.A.
Sample size: Microscopic image, 5.6 x
Photo and Owner: Milton Speckels

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