Cumengeite (original) (raw)
Formula:
Pb21Cu20Cl42(OH)40 · 6H2O
Crystal System:
Tetragonal
Name:
Named in honor of Bernard Louis Philippe Édouard Cumenge (16 April 1828, Castres, France - 20 July 1902, Paris, France), mining engineer at Boleo, Mexico. He collected the first specimens.
A secondary mineral.
May be confused with diaboleite.
Correct spelling defined by Burke (2008); other, incorrect spelling is cumengéite.
Cleavage:
Distinct/Good
{101} good; {110} distinct; {001} Poor.
Density:
4.656 g/cm3 (Measured) 4.66 g/cm3 (Calculated)
RI values:
_n_ω = 2.026 - 2.041 _n_ε = 1.926 - 1.965
δ = 0.100
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
Comments:
Dichroic.
O = darker blue with green tint
E = Pure blue
Crystal System:
Tetragonal
Class (H-M):
4/m m m _(_4/_m_2/_m_2/m ) - Ditetragonal Dipyramidal
Cell Parameters:
a = 15.065(2) Å, c = 24.436(5) Å
Unit Cell V:
5,545.85 ų (Calculated from Unit Cell)
Morphology:
Octahedral or cubo-octahedral crystals. Commonly on the faces of boleite or pseudoboleite.
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| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0014482 | Cumengeite | Hawthorne F C, Groat L A (1986) The crystal structure and chemical composition of cumengeite Mineralogical Magazine 50 157-162 |  |
1986 | Boleo, Baja California, Mexico | 0 | 293 |
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Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
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.
- 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.