Cumengite Mineral Data

General Cumengite Information

Chemical Formula:

Cu20Pb21Cl42(OH)40•6H2O

Composition:

Molecular Weight = 7,899.52 gm

Copper 16.09 % Cu 20.14 % CuO

Hydrogen 0.66 % H 5.93 % H₂O

Lead 55.08 % Pb 59.34 % PbO

Chlorine 18.85 % Cl 18.85 % Cl

- % Cl -4.25 % -O=Cl₂

Oxygen 9.32 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Cu₂₀Pb₂₁Cl₄₂(OH)₄₀•6(H₂O)

Environment:

Oxidized zone of sedimentary copper ores associated with boleite.

IMA Status:

Valid Species (Pre-IMA) 1893

Locality:

Boleo, near Santa Rosalia, Baja California Sur. Link to MinDat.org Location Data.

Name Origin:

Named for Edouard Cumenge (1828-1902), French mining engineer for the Boleo mines.

Synonym:

Cumengeite

Cumengite Image

Images:

Cumengite Boleite

Comments: Inky blue cumengite "sixling" epitaxially overgrown on boleite.
Location: Amelia mine, Santa Rosalia, Baja California Sur, Mexico. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Cumengite Crystallography

Axial Ratios:

a:c = 1:1.62204

Cell Dimensions:

a = 15.1007, c = 24.494, Z = 2; V = 5,585.40 Den(Calc)= 4.70

Crystal System:

Tetragonal - Ditetragonal Dipyramidal H-M Symbol (4/m 2/m 2/m) Space Group: I 4/mmm

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

By Intensity(I/I_o): 2.372(1), 4.83(0.9), 2.657(0.8),

Physical Properties of Cumengite

Cleavage:

{101} Distinct, {110} Poor

Color:

Indigo blue.

Density:

4.67

Diaphaneity:

Transparent

Fracture:

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.

Habit:

Epitaxial - Crystallographic alignment with a precursor mineral

Habit:

Pseudo Cubic - Crystals show a cubic outline.

Hardness:

2.5 - Finger Nail

Luster:

Adamantine

Streak:

blue

Optical Properties of Cumengite

Gladstone-Dale:

CI meas= -0.092 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= -0.085 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2093,KPDmeas= 0.2106,KC= 0.1929
Ncalc = 1.9 - 1.91

Optical Data:

Uniaxial (-), e=1.926, w=2.041, bire=0.1150.

Calculated Properties of Cumengite

Electron Density:

Bulk Density (Electron Density)=4.09 gm/cc
note: Specific Gravity of Cumengite =4.70 gm/cc.

Fermion Index:

Fermion Index = 0.12
Boson Index = 0.88

Photoelectric:

PE_Cumengite= 981.17 barns/electron
U=PE_Cumengite x rElectron Density=4,011.66 barns/cc.

Radioactivity:

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

Cumengite Classification

Dana Class:

10.06.07.01 (10)Oxyhalides and Hydroxyhalides

(10.06)where Am Bn (O,OH)p Xq

(10.06.07)Dana Group

10.06.07.01 Cumengite Cu20Pb21Cl42(OH)40•6H2O I 4/mmm 4/m 2/m 2/m

Strunz Class:

03.DB.20 03 - HALIDES

03.D - Oxyhalides, Hydroxyhalides and Related Double Halides

03.DB -With Pb, Cu, etc.

03.DB.20 Cumengite Cu20Pb21Cl42(OH)40•6H2O I 4/mmm 4/m 2/m 2/m

Other Cumengite Information

References:

NAME( Ford32) PHYS. PROP.(Dana8, AmMin v91, p1208) OPTIC PROP.(Ford32)

See Also:

Links to other databases for Cumengite :
1 - Am. Min. Crystal Structure Database
2 - Amethyst Galleries' Mineral Gallery
3 - Athena
4 - EUROmin Project
5 - Ecole des Mines de Paris
6 - GeoScienceWorld
7 - Google Images
8 - Google Scholar
9 - MinDAT
10 - Mineralienatlas (Deutsch)
11 - Online Mineral Museum
12 - QUT Mineral Atlas
13 - Ruff.Info

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

Cumengite

Cu20Pb21Cl42(OH)40•6H2O
Dana No: 10.06.07.01 Strunz No: 03.DB.20
Locality:

Notes:

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