Geminite Mineral Data

Geminite Mineral Data +

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General Geminite Information

Chemical Formula:

Cu++2As+++++2O7·3(H2O)

Composition:

Molecular Weight = 442.98 gm

Copper 28.69 % Cu 35.91 % CuO

Arsenic 33.83 % As 51.89 % As₂O₅

Hydrogen 1.37 % H 12.20 % H₂O

Oxygen 36.12 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Cu₂As₂O₇·3(H₂O)

Environment:

Coatings on quartz.

IMA Status:

Approved IMA 1990

Locality:

Cap Garonne mine, Var, France. Link to MinDat.org Location Data.

Name Origin:

Named from the Latin gemini, twins, in allusion to the usual character of the crystals.

Synonym:

ICSD 81587

IMA1988-045

PDF 44-1454

Trichalcite

Geminite Image

Images:

Geminite

Comments: Pale greenish crystals of geminite with a light blue, lavendulane-related mineral.
Location: Shaft 371, Schlema-Hartenstein area, Erzgebirge, Saxony, Germany. Scale: Picture size 4 mm.
© Thomas Witzke / Abraxas-Verlag

Geminite Crystallography

Axial Ratios:

a:b:c =0.8186:1:1.9398

Cell Dimensions:

a = 6.639, b = 8.11, c = 15.732, Z = 4; alpha = 92.01°, beta = 93.87°, gamma = 95.02° V = 841.36 Den(Calc)= 3.50

Crystal System:

TriclinicSpace Group: P1 or P1

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 7.83(1), 3.07(0.7), 3.26(0.7),

Crystal Structure:

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Cooper M A , Hawthorne F C , The Canadian Mineralogist , 33 (1995) p.1111-1118, The crystal structure of geminite, Cu(AsO3OH)(H2O), a heteropolyhedral sheet, structure

Physical Properties of Geminite

Cleavage:

[001] Perfect

Color:

Light green, Sea green.

Density:

3.7 - 3.71, Average = 3.7

Diaphaniety:

Transparent

Fracture:

Irregular - Flat surfaces (not cleavage) fractured in an irregular pattern.

Habit:

Columnar - Forms columns

Habit:

Radial - Crystals radiate from a center without producing stellar forms (e.g. stibnite)

Habit:

Twinning Common - Crystals are usually twinned.

Hardness:

3-3.5 - Calcite-Copper Penny

Luminescence:

Non-fluorescent.

Luster:

Vitreous (Glassy)

Magnetism:

Nonmagnetic

Streak:

pale green

Optical Properties of Geminite

Gladstone-Dale:

CI meas= -0.021 (Excellent) - where the CI = (1-KPDmeas/KC)
CI calc= -0.081 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2017,KPDmeas= 0.1906,KC= 0.1866

Optical Data:

Biaxial (+), a=1.656, b=1.692, g=1.77, bire=0.1140, 2V(Calc)=72, 2V(Meas)=75. Dispersion weak, r > v.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

green pale grayish.

Calculated Properties of Geminite

Electron Density:

r_electron=3.51 gm/cc
note: r_Geminite=3.71 gm/cc.

Fermion Index

Fermion Index = 0.00017
Boson Index = 0.99983

Photoelectric:

PE_Geminite= 35.88 barns/electron
U=PE_Geminite x r_electron= 126.04 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Geminite is Not Radioactive

Geminite Classification

Dana Class:

40.5.12.1 (40)Hydrated Phosphates, etc

(40.5)with miscellaneous formulae

(40.5.12)Dana Group

40.5.12.1 Geminite Cu2As2O7·3(H2O) P1 or P1 Tri

40.5.12.2 Pushcharovskite! Cu(AsO3OH)·1.5(H2O) P1 or P1 Tri

Strunz Class:

VII/C.06-30 VII - Phosphates, Arsenates and Vanadates

VII/C - Water-bearing phosphates without unfamiliar anions. cations of medium and small size: Be and Mn, Fe, Cu, Zn, Mg

VII/C.06 - Cobaltkoritnigite - Geigerite series

VII/C.06-10 Cobaltkoritnigite (Co,Zn)(AsO3OH)·(H2O) P1 1

VII/C.06-20 Koritnigite ZnHAsO4·(H2O) P1 1

VII/C.06-30 Geminite Cu2As2O7·3(H2O) P1 or P1 Tri

VII/C.06-32 Pushcharovskite! Cu(AsO3OH)·1.5(H2O) P1 or P1 Tri

VII/C.06-35 Yvonite! Cu(AsO3OH)·2(H2O) P1 1

VII/C.06-37 Rollandite! Cu3(AsO4)2·4(H2O) P nma 2/m 2/m 2/m

VII/C.06-40 Chudobaite (Mg,Zn)5(AsO3OH)2(AsO4)2·10(H2O) P1 1

VII/C.06-50 Lindackerite CuCu4(AsO4)2(AsO3OH)2·~9(H2O) P1 1

VII/C.06-60 Geigerite Mn5(AsO3OH)2(AsO4)2·10(H2O) P1 1

Other Geminite Information

References:

NAME( Dana8) PHYS. PROP.(Dana8) OPTIC PROP.(Dana8)

See Also:

Links to other databases for Geminite :
1 -Am. Min. Crystal Structure Database 2 -Athena 3 - EUROmin Project 4 -Google Images 5 -Google Scholar 6 -Handbook of Mineralogy (UofA) 7 -MinDAT 8 -MinMax(Deutsch) 9 -MinMax(English) 10 -Mineralienatlas (Deutsch) 11 -QUT Mineral Atlas 12 - WWW-MINCRYST 13 -École des Mines de Paris

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Print or Cut-and-Paste your Geminite Specimen Label here :

Geminite

Cu++2As+++++2O7·3(H2O)
Dana No: 40.5.12.1 Strunz No: VII/C.06-30
Locality:

Notes: