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About GeminiteHide

Cu2+(AsO3OH) · H2O
Also written as Cu(HAsO4).H2O.
Light green to sea green
3 - 3½
Specific Gravity:
Crystal System:
Named by H. Sarp and P. Perroud in 1990. The name is derived from the Latin gemini, meaning twins, for the twinning observed in the mineral.
Chemically and structurally close to krupičkaite.

Classification of GeminiteHide

Approval year:
First published:

C : Phosphates without additional anions, with H2O
B : With only medium-sized cations, RO4:H2O = 1:1

5 : AXO4·xH2O

20 : Arsenates (also arsenates with phosphate, but without other anions)
1 : Arsenates of Cu

Physical Properties of GeminiteHide

Light green to sea green
Pale green
3 - 3½ on Mohs scale
3.70(2) g/cm3 (Measured)    3.71 g/cm3 (Calculated)

Optical Data of GeminiteHide

Biaxial (+)
RI values:
nα = 1.656 nβ = 1.692 nγ = 1.770
Measured: 75° , Calculated: 72°
Max Birefringence:
δ = 0.114
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Surface Relief:
α = β = colorless
γ = pale green to pale gray

Chemical Properties of GeminiteHide

Cu2+(AsO3OH) · H2O

Also written as Cu(HAsO4).H2O.

Crystallography of GeminiteHide

Crystal System:
Cell Parameters:
a = 6.63 Å, b = 8.11 Å, c = 15.73 Å
α = 92.01°, β = 93.87°, γ = 95.02°
a:b:c = 0.818 : 1 : 1.94
Unit Cell V:
839.91 ų (Calculated from Unit Cell)
Tabular {001}, slightly elongate [100].
Twinned polysynthetically parallel to {001}.

Crystal StructureHide

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IDSpeciesReferenceLinkYearLocalityPressure (GPa)Temp (K)
0005467GeminiteCooper M A, Hawthorne F C (1995) The crystal structure of geminite, Cu(AsO3OH)(H2O), a heteropolyhedral sheet structure The Canadian Mineralogist 33 1111-11181995Cap Garone, France0293
0014670GeminitePrencipe M, Pushcharovsky D Y, Sarp H, Ferraris G (1996) Comparative crystal chemistry of geminite Cu[AsO3OH]H2O and related minerals Moscow University Geology Bulletin 51 51-581996Salsigne mine, Carrassonne, Aude, France0293
CIF Raw Data - click here to close

X-Ray Powder DiffractionHide

Powder Diffraction Data:
7.83 Å(100)
3.925 Å(60)
3.260 Å(70)
3.107 Å(40)
3.070 Å(70)
2.825 Å(40)
2.611 Å(50)

Type Occurrence of GeminiteHide

Place of Conservation of Type Material:
Museum d'Histoire Naturelle de Geneve, Geneva, Switzerland.
Associated Minerals at Type Locality:
Sarp, H., Perroud, P. (1990) La geminite, Cu2As2O7·3H2O, un nouveau minéral de la mine de Cap Garonne, Var, France. Schweizerische Mineralogische und Petrographische Mitteilungen: 70: 309-314.

Synonyms of GeminiteHide

Other Language Names for GeminiteHide


Common AssociatesHide

Associated Minerals Based on Photo Data:
22 photos of Geminite associated with YvoniteCu(HAsO4) · 2H2O
8 photos of Geminite associated with PushcharovskiteK0.6Cu18(AsO4)(HAsO4)10(H2AsO4)4(OH)9.6 · 18.6H2O
7 photos of Geminite associated with BismuthBi
2 photos of Geminite associated with QuartzSiO2
2 photos of Geminite associated with RapidcreekiteCa2(SO4)(CO3) · 4H2O
1 photo of Geminite associated with ArsenoliteAs2O3

Related Minerals - Nickel-Strunz GroupingHide

8.CB.05SerrabrancaiteMnPO4 · H2OMon. 2/m : B2/b
8.CB.10HureauliteMn2+5(PO3OH)2(PO4)2 · 4H2OMon. 2/m : B2/b
8.CB.10SainfelditeCa5(AsO4)2(AsO3OH)2 · 4H2OMon. 2/m : B2/b
8.CB.10VillyaelleniteMnMn2Ca2(AsO4)2(HAsO4)2 · 4H2OMon. 2/m : B2/b
8.CB.10UM1997-09-AsO:CaHMgZn(Mg,Ca,Zn)5(AsO4)2(HAsO4)2 · 4H2OMon.
8.CB.10NyholmiteCd3Zn2(AsO4)2(HAsO4)2 · 4H2OMon. 2/m : B2/b
8.CB.10MiguelromeroiteMnMn2Mn2(AsO4)2(HAsO4)2 · 4H2OMon. 2/m : B2/b
8.CB.15FluckiteCaMn2+(AsO3OH)2 · 2H2OTric. 1 : P1
8.CB.15KrautiteMn(HAsO4) · H2OMon. 2 : P21
8.CB.20Cobaltkoritnigite(Co,Zn)(HAsO4) · H2OTric. 1 : P1
8.CB.20KoritnigiteZn(HAsO4) · H2OTric. 1 : P1
8.CB.25YvoniteCu(HAsO4) · 2H2OTric.
8.CB.35SchubneliteFe3+VO4 · H2OTric.
8.CB.40RadovaniteCu2Fe3+(AsO4)(HAs3+O3)2 · H2OOrth. mmm (2/m 2/m 2/m) : Pnma
8.CB.45KazakhstaniteFe3+5V4+3V5+12O39(OH)9 · 9H2OMon.
8.CB.50KolovratiteNixZny(VO4)0.67(x+y) · nH2O
8.CB.55IrhtemiteCa4Mg(AsO4)2(HAsO4)2 · 4H2OMon.
8.CB.60BurgessiteCo2(H2O)4[AsO3(OH)]2(H2O)Mon. 2/m

Related Minerals - Hey's Chemical Index of Minerals GroupingHide

20.1.2OliveniteCu2(AsO4)(OH)Mon. 2/m : P21/m
20.1.3ClinoclaseCu3(AsO4)(OH)3Mon. 2/m : P21/b
20.1.4CornwalliteCu5(AsO4)2(OH)4Mon. 2/m : P21/b
20.1.5CornubiteCu5(AsO4)2(OH)4Tric. 1 : P1
20.1.6Chlorotile (of Frenzel)
20.1.8EuchroiteCu2(AsO4)(OH) · 3H2OOrth. 2 2 2 : P21 21 21
20.1.9StrashimiriteCu8(AsO4)4(OH)4 · 5H2OMon.
20.1.10ArhbariteCu2Mg(AsO4)(OH)3Tric. 1 : P1
20.1.11LindackeriteCuCu4(AsO4)2(HAsO4)2 · 9H2OTric. 1 : P1
20.1.12ConichalciteCaCu(AsO4)(OH)Orth. 2 2 2 : P21 21 21
20.1.13LiroconiteCu2Al(AsO4)(OH)4 · 4H2OMon. 2/m
20.1.14CeruleiteCu2Al7(AsO4)4(OH)13 · 11.5H2OMon.
20.1.15ChenevixiteCu2Fe3+2(AsO4)2(OH)4Mon. 2/m : P21/m
20.1.16ArthuriteCuFe3+2(AsO4)2(OH)2 · 4H2OMon.

Fluorescence of GeminiteHide

Other InformationHide

Thermal Behaviour:
On heating, the mineral becomes anhydrous between 200°C and 250°C.
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 GeminiteHide

Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Sarp, H., Perroud, P. (1990) La geminite, Cu2As2O7·3H2O, un nouveau minéral de la mine de Cap Garonne, Var, France. Schweizerische Mineralogische und Petrographische Mitteilungen: 70: 309-314.
Jambor, J.L. (1992) New mineral names. American Mineralogist: 77: 670-675.
Cooper, M.A., Hawthorne, F.C. (1995) The crystal structure of geminite, Cu2+(AsO3OH)(H2O), a heteropolyhedral sheet structure. The Canadian Mineralogist: 33: 1111-1118.
Prencipe, M., Pushcharovsky, D.Y., Sarp, H., Ferraris, G. (1996) Comparative crystal chemistry of geminite Cu[AsO3OH]H2O and related minerals. Moscow University Geology Bulletin: 51: 51-58.
Jambor, J.L., Pertsev, N.N., Roberts, A.C. (1996) New mineral names. American Mineralogist: 81: 766-770.
New Minerals (1997), New Minerals 1990-1994.
Jambor, J.L., Pertsev, N.N., Roberts, A.C. (1998) New mineral names. American Mineralogist: 83: 907-911.
Plumhoff, A.M., Plášil, J., Dachs, E., Benisek, A., Sejkora, J., Števko, M., Rumsey, M.S., Majzlan, J. (2020) Thermodynamic properties, crystal structure and phase relations of pushcharovskite [Cu(AsO3OH)(H2O) ⋅ 0.5H2O], geminite [Cu(AsO3OH)(H2O)] and liroconite [Cu2Al(AsO4)(OH)4 ⋅ 4H2O]. European Journal of Mineralogy: 32: 285–304.

Internet Links for GeminiteHide

Localities for GeminiteHide

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 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 (eg from pseudomorphs.)

All localities listed without proper references should be considered as questionable.
Czech Republic
  • Karlovy Vary Region
    • Karlovy Vary District
      • Jáchymov
Lapis 2002(7/8), 54
Lapis 2002(7/8), 54
  • Occitanie
    • Aude
      • Carcassonne
        • Salsigne
[AmMin 84:197]
  • Provence-Alpes-Côte d'Azur
    • Var
      • Le Pradet
Schweiz.Min.Petr.Mitt.(1990) 70, 309-314
  • Saxony
    • Zwickau district
      • Hartenstein
Lapis 1994(10), 36-39
  • Attica
    • East Attica
      • Lavreotiki
        • Lavrion mining district
          • Agios Konstantinos (Kamariza)
            • Mercati mines
Rieck, B., Kolitsch, U., Voudouris, P., Giester, G. and Tzeferis, P. (2018): Weitere Neufunde aus Lavrion, Griechenland. Mineralien-Welt 29 (5), 32-77 (in German).
  • Sardinia
    • South Sardinia Province
      • Gonnosfanadiga
        • Fenugu Sibiri Mine
Caboni, F., Mamberti, M., Tanca, G.A., Vinci, A., Bittarello, E., Marengo, A., Brizio, P., Bracco, R., Baralis, L., Desor, J., Ciriotti, M.E. (2018): Arseniati, arseniuri e altre novità di Pira Inferida - Fenugu Sibiri, Gonnosfanadiga, Sud Sardegna. Micro, 16, 110-156 (in Italian with abstracts in English, French and German).
  • Drâa-Tafilalet Region
    • Ouarzazate Province
      • Amerzgane Cercle
        • Ouisselsate Caïdat
Favreau, G. and Dietrich, J. E. (2006). Die Mineralien von Bou Azzer. Lapis 31(7/8), 27-68
  • Oshikoto Region
    • Tsumeb
Hawthorne et al. (2011) Davidlloydite, ideally Zn3(AsO4)2(H2O)4, a new arsenate mineral from the Tsumeb mine, Otjikoto (Oshikoto) region, Namibia. Mineralogical Magazine 76(1): 45–57.
  • Lower Silesian Voivodeship
    • Lubin County
      • Gmina Lubin
Material analysed by University of Silesia Łukasz Kruszewski PXRD & EPMA data (2018).
Mineral and/or Locality  
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