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Guanacoite

A valid IMA mineral species
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08962340014966468319378.jpg
Guanacoite

Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
05083930014946998512285.jpg
Guanacoite

Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
09298940014950863101732.jpg
Guanacoite, etc.

Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
00178490014961106075908.jpg
Guanacoite

Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
09548710014969846437559.jpg
Guanacoite

Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
09298940014950863101732.jpg
Guanacoite, etc.

Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
08962340014966468319378.jpg
Guanacoite

Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
06994190014946998513961.jpg
Guanacoite

Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
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About GuanacoiteHide

05230350015151677245416.jpg
Entry of the underground mine

Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
Formula:
Cu2Mg3(AsO4)2(OH)4 · 4H2O
Colour:
Blue to pale blue
Lustre:
Vitreous
Hardness:
3
Specific Gravity:
3.31
Crystal System:
Monoclinic
Name:
Named for El Guanaco mine, Chile, the type locality.
A rare secondary Cu-Mg arsenate, isotypic with akrochordite.

The Mg analogue of vargite.

The Cu:Mg ratios on the three Cu/Mg sites in the crystal structure were shown to be variable and a Mg-dominant member has been reported by Kyono (2008), but not proposed as a new mineral species yet.



Unique IdentifiersHide

Mindat ID:
11511
Long-form identifier:
mindat:1:1:11511:3
GUID
(UUID V4):
70ce0f5c-9fcf-43d1-b9b1-df10c678dc5d

IMA Classification of GuanacoiteHide

Classification of GuanacoiteHide

Strunz-mindat (2024):
8.DD.10

8 : PHOSPHATES, ARSENATES, VANADATES
D : Phosphates, etc. with additional anions, with H2O
D : With only medium-sized cations, (OH, etc.):RO4= 2:1
Dana 8th ed.:
42.4.1.2

42 : HYDRATED PHOSPHATES, ETC.CONTAINING HYDROXYL OR HALOGEN
4 : (AB)5(XO4)2Zq·xH2O

Mineral SymbolsHide

As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.

SymbolSourceReference
GncIMA–CNMNCWarr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43

Physical Properties of GuanacoiteHide

Lustre:
Vitreous
Transparency:
Transparent
Colour:
Blue to pale blue
Streak:
White to pale blue
Hardness:
3 on Mohs scale
Hardness Data:
Estimated
Tenacity:
Brittle
Cleavage:
Distinct/Good
Parallel to {010}
Fracture:
Irregular/Uneven, Conchoidal
Density:
3.31 g/cm3 (Measured)    3.36 g/cm3 (Calculated)
Comment:
The calculated density refers to the ideal composition; the average Cu/Mg ratio measured by microprobe leads to a density of 3.30 g/cm3

Optical Data of GuanacoiteHide

Type:
Biaxial (-)
RI values:
nα = 1.664(1) nβ = 1.691(1) nγ = 1.695(1)
2V:
Measured: 31° , Calculated: 42°
Max Birefringence:
δ = 0.031
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
High
Dispersion:
r > v, weak
Optical Extinction:
X ∼ c; Y ∧ a = 10° (in obtuse β); Z = b.
Pleochroism:
Non-pleochroic

Chemistry of GuanacoiteHide

Mindat Formula:
Cu2Mg3(AsO4)2(OH)4 · 4H2O
Elements listed:
As, Cu, H, Mg, O - search for minerals with similar chemistry

Crystallography of GuanacoiteHide

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Cell Parameters:
a = 5.475(1) Å, b = 16.865(3) Å, c = 6.915(1) Å
β = 99.8(3)°
Ratio:
a:b:c = 0.325 : 1 : 0.41
Unit Cell V:
629.2 ų
Z:
2
Morphology:
Type material is prismatic and elongated along [100]. The dominant form is {031}, terminated by {120}. The forms {111} and {121} are rare.
The crystals from Taghouni are elongated on [100], showing dominant prism {021} and terminated by {100}.
Twinning:
None observed.
Comment:
Cell parameters from single-crystal data

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0004532GuanacoiteKyono A (2008) Compositional variability and crystal structural features of guanacoite American Mineralogist 93 501-5072008El Guanaco mine, Chile0293
CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

Powder Diffraction Data:
d-spacingIntensity
8.421 Å(100)
5.399 Å(38)
5.141 Å(17)
4.473 Å(17)
4.331 Å(38)
4.211 Å(24)
3.403 Å(21)
3.081 Å(28)
3.019 Å(18)
2.910 Å(35)
2.737 Å(35)
2.677 Å(25)
2.666 Å(19)
2.281 Å(23)
2.215 Å(18)
Comments:
Calculated data (measured data show preferred orientation due to cleavage).

Geological EnvironmentHide

Paragenetic Mode(s):
Paragenetic ModeEarliest Age (Ga)
Stage 7: Great Oxidation Event<2.4
47a : [Near-surface hydration of prior minerals]
47d : [Arsenates, antimonates, selenates, bismuthinates]

Type Occurrence of GuanacoiteHide

Type Locality:
ⓘ Guanaco Mine, Taltal, Antofagasta Province, Antofagasta, Chile
General Appearance of Type Material:
Prismatic to acicular crystals up to 0.7 mm in length.
Place of Conservation of Type Material:
Mineralogical Collection of the Bergakademie Freiberg, Germany, No. 79704.
Associated Minerals at Type Locality:
QuartzOliveniteEnargiteConichalciteChrysocolla
BrochantiteArhbarite
Reference:
Witzke, T., Kolitsch, U., Krause, W., Wiechowski, A., Medenbach, O., Kampf, A.R., Steele, I.M., Favreau, G. (2006) Guanacoite, Cu2Mg2(Mg0.5Cu0.5(OH)4(H2O)4(AsO4)2, a new arsenate mineral species from the El Guanaco Mine, near Taltal, Chile: Description and crystal structure. European Journal of Mineralogy: 18: 813-821.
Download:
https://rruff.info/rruff_1.0/uploads/EJM18_813.pdf

Synonyms of GuanacoiteHide

Other Language Names for GuanacoiteHide

German:Guanacoit
Spanish:Guanacoita

Relationship of Guanacoite to other SpeciesHide

Member of:
Akrochordite Group
Other Members of this group:
Akrochordite(Mn2+,Mg)5(AsO4)2(OH)4 · 4H2OMon. 2/m : P21/b
VargiteCu2Mn3(AsO4)2(OH)4(H2O)4Mon. 2/m : P21/b

Common AssociatesHide

Associated Minerals Based on Photo Data:
17 photos of Guanacoite associated with ArhbariteCu2Mg(AsO4)(OH)3
11 photos of Guanacoite associated with ConichalciteCaCu(AsO4)(OH)
6 photos of Guanacoite associated with DolomiteCaMg(CO3)2
5 photos of Guanacoite associated with EnargiteCu3AsS4
4 photos of Guanacoite associated with QuartzSiO2
1 photo of Guanacoite associated with CalciteCaCO3

Related Minerals - Strunz-mindat GroupingHide

8.DD.Bettertonite[Al6(AsO4)3(OH)9(H2O)5] · 11H2OMon. 2/m : P21/b
8.DD.Penberthycroftite[Al6(AsO4)3(OH)9(H2O)5] · 8H2OMon. 2/m : P21/b
8.DD.VargiteCu2Mn3(AsO4)2(OH)4(H2O)4Mon. 2/m : P21/b
8.DD.GaleaclolusiteAl6(AsO4)3(OH)9(H2O)4 · 8H2OOrth. mmm (2/m 2/m 2/m) : Pnma
8.DD.05ChenevixiteCu2Fe3+2(AsO4)2(OH)4Mon. 2/m : P21/m
8.DD.05LuetheiteCu2Al2(AsO4)2(OH)4Mon. 2/m : P21/m
8.DD.10Akrochordite(Mn2+,Mg)5(AsO4)2(OH)4 · 4H2OMon. 2/m : P21/b
8.DD.15Aheylite(Fe2+,Zn)Al6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15ChalcosideriteCuFe3+6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15CoeruleolactiteTric. 1 : P1
8.DD.15FaustiteZnAl6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15PlaneriteAl6(PO4)2(PO3OH)2(OH)8 · 4H2OTric. 1 : P1
8.DD.15TurquoiseCuAl6(PO4)4(OH)8 · 4H2OTric. 1 : P1
8.DD.15AfmiteAl3(OH)4(H2O)3(PO4)(PO3OH) · H2OTric. 1 : P1
8.DD.15UM1981-32-PO:FeHFe2+Fe3+6(PO4)4-x[PO3(OH)]x(OH)8 · 4H2O
8.DD.20ChildreniteFe2+Al(PO4)(OH)2 · H2OOrth. mm2 : Ccc2
8.DD.20EosphoriteMn2+Al(PO4)(OH)2 · H2OOrth. mmm (2/m 2/m 2/m) : Cmca
8.DD.20Ernstite(Mn2+,Fe3+)Al(PO4)(OH,O)2 · H2OMon.
8.DD.20LefontiteFe2Al2Be(PO4)2(OH)6Orth. mmm (2/m 2/m 2/m) : Cmca
8.DD.25KobokoboiteAl6(PO4)4(OH)6 · 11H2O Tric.
8.DD.30SmamiteCa2Sb(OH)4[H(AsO4)2] · 6H2OTric. 1 : P1
8.DD.35GutsevichiteAl3(PO4)2(OH)3 · 8H2OIso.
8.DD.40Laubmannite (of Moore)(Fe3+,Fe2+,M)8+x(OH,H2O)9(H2O)2(PO4)5, M = Fe3+, Cu2+ or other metal cation, x ~ 0.1.Orth. mmm (2/m 2/m 2/m) : Pbcm

Other InformationHide

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

Internet Links for GuanacoiteHide

References for GuanacoiteHide

Localities for GuanacoiteHide

This map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.

Locality ListHide

- This locality has map coordinates listed. - This locality has estimated coordinates. ⓘ - Click for references and further information on this occurrence. ? - Indicates mineral may be doubtful at this locality. - Good crystals or important locality for species. - World class for species or very significant. (TL) - Type Locality for a valid mineral species. (FRL) - First Recorded Locality for everything else (eg varieties). Struck out - Mineral was erroneously reported from this locality. Faded * - Never found at this locality but inferred to have existed at some point in the past (e.g. from pseudomorphs).

All localities listed without proper references should be considered as questionable.
Chile (TL)
 
  • Antofagasta
    • Antofagasta Province
      • Taltal
Witzke et al. (2006)
Morocco
 
  • Drâa-Tafilalet Region
    • Ouarzazate Province
      • Amerzgane Cercle
        • Ouisselsate Caïdat
Witzke et al. (2006)
Spain
 
  • Andalusia
    • Almería
      • Benahadux
www.foro-minerales.com (n.d.)
      • Huércal de Almería
www.mindat.org (n.d.)
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