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Paratacamite

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Formula:
Cu3(Cu,Zn)(OH)6Cl2
System:
Trigonal
Colour:
Green to greenish-black.
Lustre:
Vitreous
Hardness:
3
Member of:
Name:
Named for its relationship to atacamite.
Atacamite Group.
A secondary copper mineral. Easily confused with the closely related Clinoatacamite and Anatacamite.

Derivatives are paratacamite-(Mg) and paratacamite-(Ni).

Also closely related to Herbertsmithite and Gillardite (both have halved a-axes by comparison to paratacamite).
On heating paratacamite reversibly transforms into herbertsmithite between 353 and 393 K (Welch et al., 2014).

Paratacamite contains essential zinc; therefore it is not a polymorph of atacamite.

"Ni-bearing paratacamite": compare Gillardite.

Classification of Paratacamite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
3.DA.10c

3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
A : With Cu, etc., without Pb
Dana 7th ed.:
10.1.2.1
10.1.2.1

10 : OXYHALIDES AND HYDROXYHALIDES
1 : A2(O,OH)3Xq
8.2.5

8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
2 : Halides of Cu
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First Recorded Occurrence of Paratacamite

Year of Discovery:
1906
Associated Minerals at First Recorded Locality:

Occurrences of Paratacamite

Geological Setting:
Oxidized zones of copper deposits, especially in arid climates.

Physical Properties of Paratacamite

Vitreous
Diaphaneity (Transparency):
Translucent
Colour:
Green to greenish-black.
Streak:
Green
Hardness (Mohs):
3
Cleavage:
Distinct/Good
Good on {10_11}
Fracture:
Irregular/Uneven, Conchoidal
Density:
3.74 g/cm3 (Measured)    3.75 g/cm3 (Calculated)

Crystallography of Paratacamite

Crystal System:
Trigonal
Class (H-M):
3m (3 2/m) - Hexagonal Scalenohedral
Cell Parameters:
a = 13.65Å, c = 13.95Å
Ratio:
a:c = 1 : 1.022
Unit Cell Volume:
V 2,250.97 ų (Calculated from Unit Cell)
Morphology:
Rhombohedral. Granular massive.
Twinning:
On {10_11} common; polysynthetic at times.

Optical Data of Paratacamite

Type:
Uniaxial (+)
RI values:
nω = 1.843 nε = 1.848
Max Birefringence:
δ = 0.005
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Very High
Pleochroism:
Non-pleochroic

Chemical Properties of Paratacamite

Formula:
Cu3(Cu,Zn)(OH)6Cl2
Essential elements:
All elements listed in formula:
Common Impurities:
Zn

Relationship of Paratacamite to other Species

Member of:
Other Members of Group:
AnatacamiteCu2(OH)3Cl
AtacamiteCu2(OH)3Cl
BotallackiteCu2(OH)3Cl
ClinoatacamiteCu2(OH)3Cl
GillarditeCu3Ni(OH)6Cl2
HaydeeiteCu3Mg(OH)6Cl2
HerbertsmithiteCu3Zn(OH)6Cl2
IyoiteMnCuCl(OH)3
KapellasiteCu3Zn(OH)6Cl2
LeverettiteCu3Co(OH)6Cl2
MisakiiteCu3Mn(OH)6Cl2
Paratacamite-(Mg)Cu3(Mg,Cu)(OH)6Cl2
Paratacamite-(Ni)Cu3(Ni,Cu)(OH)6Cl2
TondiiteCu3Mg(OH)6Cl2
Common Associates:
3.DA.05MelanothalliteCu2Cl2O
3.DA.10aAtacamiteCu2(OH)3Cl
3.DA.10bBotallackiteCu2(OH)3Cl
3.DA.10bClinoatacamiteCu2(OH)3Cl
3.DA.10aHibbingiteFe22+(OH)3Cl
3.DA.10aKempiteMn22+(OH)3Cl
3.DA.10bBelloiteCu(OH)Cl
3.DA.10cHerbertsmithiteCu3Zn(OH)6Cl2
3.DA.10cKapellasiteCu3Zn(OH)6Cl2
3.DA.10cGillarditeCu3Ni(OH)6Cl2
3.DA.10cHaydeeiteCu3Mg(OH)6Cl2
3.DA.10dAnatacamiteCu2(OH)3Cl
3.DA.15ClaringbulliteCu4ClF(OH)6
3.DA.15BarlowiteCu4BrF(OH)6
3.DA.20SimonkolleiteZn5Cl2(OH)8 · H2O
3.DA.25ButtgenbachiteCu19(NO3)2(OH)32Cl4 · 2H2O
3.DA.25ConnelliteCu19(SO4)(OH)32Cl4 · 3H2O
3.DA.30AbhuriteSn21Cl16(OH)14O6
3.DA.35PonomareviteK4Cu4Cl10O
3.DA.40AnthonyiteCu(OH,Cl)2 · 3H2O
3.DA.40CalumetiteCu(OH,Cl)2 · 2H2O
3.DA.45KhaidarkaniteNa0.34Cu4Al3(OH)14F3 · 2H2O
3.DA.50BobkingiteCu5Cl2(OH)8 · 2H2O
3.DA.55AvdoniniteK2Cu5(OH)4Cl8 · H2O
3.DA.60DroninoiteNi6Fe32+(OH)16Cl2 · 4H2O
8.2.1NantokiteCuCl
8.2.2TolbachiteCuCl2
8.2.3EriochalciteCuCl2 · 2H2O
8.2.4AtacamiteCu2(OH)3Cl
8.2.6BotallackiteCu2(OH)3Cl
8.2.7MelanothalliteCu2Cl2O
8.2.8CalumetiteCu(OH,Cl)2 · 2H2O
8.2.9AnthonyiteCu(OH,Cl)2 · 3H2O
8.2.10ClaringbulliteCu4ClF(OH)6
8.2.11MarshiteCuI
8.2.12MitscherlichiteK2CuCl4 · 2H2O
8.2.13PonomareviteK4Cu4Cl10O

Other Names for Paratacamite

Name in Other Languages:

Other Information

Other Information:
Readily soluble in acids.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Paratacamite

Reference List:
Scacchi (1873) Reale accademia delle scienze fisische e matematiche, Naples: 6, no. 9: 22.

Smith (1906) Mineralogical Magazine: 14: 170.

Frondel, C. (1950) Mineralogical Magazine: 29: 34.

Palache, Charles, Harry Berman & Clifford Frondel (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 74-76.

American Mineralogist (1951): 36: 384.

Acta Crystallographica: B31: 183-187.

Pollard, A.M., Thomas, R.G., and Williams, P.A. (1989): Synthesis and stabilities of the basic copper(II) chlorides atacamite, paratacamite and botallackite. Minerlogical Magazine 53, 557-563.

Braithwaite, R.S.W., Mereiter, K., Paar, W.H. and Clark, A.M. (2004) Herbertsmithite, Cu3Zn(OH)6Cl2, a new species, and the definition of paratacamite. Mineralogical Magazine, 68, 527-539.

Malcherek, T. & Schlüter, J. (2008): The crystal structure of clinoatacamite and the quest for paratacamite. Poster, Annual Meeting of the DMG, Berlin, Germany, September 14-17, 2008; CD with abstracts, Abs. no. 527.

Shaoyan Chu (2011): Magnetic properties of geometrically frustrated polymorphic crystals of Cu4-xMgx(OH)6Cl2. J. Phys.: Conf. Ser. 273, 012123.

Welch, M.D., Sciberras, M.J., Williams, P.A., Leverett, P., Schlüter, J., Malcherek, T. (2014): A temperature-induced reversible transformation between paratacamite and herbertsmithite. Physics and Chemistry of Minerals, 41, 33-48.

Internet Links for Paratacamite

Specimens:
The following Paratacamite specimens are currently listed for sale on minfind.com.

Localities for Paratacamite

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