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Cryptomelane

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Formula:
K(Mn74+Mn3+)O16
System:
Monoclinic
Colour:
Brown, greyish-white
Lustre:
Earthy
Hardness:
5 - 6½
Name:
Named in 1942 by Wallace E. Richmond and Forrest A. Gonyer From the Greek words meaning κρυπτοζ "hidden" and ρελαζ "black," since as the identity of this common black manganese mineral has been hidden within a group of manganese oxides.
This page provides mineralogical data about Cryptomelane.

Classification of Cryptomelane

Approved 1982
4.DK.05a

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
K : With large (+- medium-sized) cations; tunnel structures
7.9.1.2

7 : MULTIPLE OXIDES
9 : AB8X16
7.2.4

7 : Oxides and Hydroxides
2 : Oxides of the alkali metals
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Type Occurrence of Cryptomelane

Physical Properties of Cryptomelane

Earthy
Colour:
Brown, greyish-white
Streak:
Brownish black
Hardness (Mohs):
5 - 6½

Crystallography of Cryptomelane

Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 9.956Å, b = 2.8705Å, c = 9.706Å
β = 90.95°
Ratio:
a:b:c = 3.468 : 1 : 3.381
Unit Cell Volume:
V 277.35 ų (Calculated from Unit Cell)
Z:
1
Comment:
Non-standard I2/m setting; pseudo-tetragonal
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:
d-spacingIntensity
2.39 (100)
6.90 (90)
4.90 (80)
3.10 (80)
2.15 (60)
1.83 (60)
1.54 (60)
Comments:
Very similar to coronadite.

Chemical Properties of Cryptomelane

Formula:
K(Mn74+Mn3+)O16
Essential elements:
All elements listed in formula:

Relationship of Cryptomelane to other Species

Other Members of Group:
CoronaditePb(Mn64+Mn23+)O16
FerrihollanditeBa(Mn64+Fe23+)O16
HollanditeBa(Mn64+Mn23+)O16
ManjiroiteNa(Mn74+Mn3+)O16
StrontiomelaneSr(Mn64+Mn23+)O16
4.DK.05Akaganeiteβ-Fe3+O(OH,Cl)
4.DK.05aCoronaditePb(Mn64+Mn23+)O16
4.DK.05aHollanditeBa(Mn64+Mn23+)O16
4.DK.05aManjiroiteNa(Mn74+Mn3+)O16
4.DK.05bMannarditeBa(Ti64+V23+)O16
4.DK.05bPrideriteK(Ti74+Fe3+)O16
4.DK.05bRedledgeiteBa(Ti64+Cr23+)O16
4.DK.05bHenrymeyeriteBa(Ti74+Fe2+)O16
4.DK.05aStrontiomelaneSr(Mn64+Mn23+)O16
4.DK.10Romanèchite(Ba,H2O)2Mn5O10
4.DK.10Todorokite(Ca,K,Na,Mg,Ba,Mn)(Mn,Mg,Al)6O12 · 3H2O
7.2.1Lithiophorite(Al,Li)MnO2(OH)2
7.2.2DiaoyudaoiteNaAl11O17
7.2.3ManjiroiteNa(Mn74+Mn3+)O16

Other Names for Cryptomelane

Other Information

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 Cryptomelane

Reference List:
Richmond, W.E. & M. Fleischer (1942), Cryptomelane, a new name for the commonest of the 'psilomelane' minerals, American Mineralogist: 27: 607-610.

Post, J. E., Von Dreele, R. B., and Buseck, P. R. (1982): Symmetry and cation displacements in hollandites: structure refinements of hollandite, cryptomelane and priderite. Acta Crystallogr.: B38: 1056-1065.

Internet Links for Cryptomelane

Localities for Cryptomelane

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.
Mineral and/or Locality  
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