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.

Name Pronunciation:

Geminite

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

Diaphaneity:

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
Ncalc = 1.65 - 1.69

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:

Bulk Density (Electron Density)=3.51 gm/cc
note: Specific Gravity of Geminite =3.71 gm/cc.

Fermion Index:

Fermion Index = 0.0001754138
Boson Index = 0.9998245862

Photoelectric:

PE_Geminite= 35.88 barns/electron
U=PE_Geminite x rElectron Density= 126.04 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Geminite is Not Radioactive

Geminite Classification

Dana Class:

40.05.12.01 (40)Hydrated Phosphates, etc

(40.05)with miscellaneous formulae

(40.05.12)Dana Group

40.05.12.01 Geminite Cu2As2O7•3(H2O) P1 or P1 Tri

40.05.12.02 Pushcharovskite! Cu(AsO3OH)•1.5(H2O) P1 or P1 Tri

Strunz Class:

08.CB.30 08 - PHOSPHATES, ARSENATES, VANADATES

08.C - Phosphates without Additional Anions, with H2O

08.CB -With only medium-sized cations, RO4:H2O = 1:1

08.CB.30 Geminite Cu2As2O7•3(H2O) P1 or P1 Tri

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 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info
15 - WWW-MINCRYST

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

Geminite

Cu++2As+++++2O7•3(H2O)
Dana No: 40.05.12.01 Strunz No: 08.CB.30
Locality:

Notes: