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Cryptomelane

Big Photo

Serra da Mina, Cercal (Cercal do Alentejo), Santiago do Cacém, Setúbal District, Portugal
© Martins da Pedra

Show Cryptomelane Photos (30)
Formula:
K(Mn
4+
 
,Mn
2+
 
)
 
8
O
 
16
System:MonoclinicColour:Brown, greyish-white
Lustre:EarthyHardness:5 - 6½
Name:From the Greek words meaning "hidden" and "black," since as the identity of this common black manganese mineral has been lost within the group of such minerals.
This page provides mineralogical data about Cryptomelane.

Classification of Cryptomelane

IMA status:Approved 1982
Strunz 8th edition ID:4/D.08-20
Nickel-Strunz 10th (pending) edition ID:4.DK.10

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
Dana 8th edition ID:7.9.1.2

7 : MULTIPLE OXIDES
9 : AB8X16
Hey's CIM Ref.:7.2.4

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

Type Locality:Tombstone, Tombstone District, Tombstone Hills, Cochise Co., Arizona, USA

Physical Properties of Cryptomelane

Lustre: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:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data: Peaks:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction:
d-spacingIntensity
2.39 (100)
6.90 (90)
4.90 (80)
3.10 (80)
2.15 (60)
1.83 (60)

Chemical Properties of Cryptomelane

Formula:
K(Mn
4+
 
,Mn
2+
 
)
 
8
O
 
16
Essential elements:K, Mn, O
All elements listed in formula:K, Mn, O

Relationship of Cryptomelane to other Species

Member of Group:
Cryptomelane Group:
Related Minerals - Nickel-Strunz Grouping):

- +
4.DK.05Akaganeite
β-Fe
3+
 
O(OH,Cl)
4.DK.05Ankangite
Ba(Ti,V
3+
 
,Cr)
 
8
O
 
16
4.DK.05Coronadite
Pb(Mn,Mn)
 
8
O
 
16
4.DK.05Hollandite
Ba(Mn
4+
 
,Mn
2+
 
)
 
8
O
 
16
4.DK.05Manjiroite
(Na,K)Mn
 
8
O
 
16
·nH
 
2
O
4.DK.05Mannardite
Ba
 
x
Ti
 
8-2x
V
 
2x
O
 
16
·2-xH
 
2
O
4.DK.05Priderite
(K,Ba)(Ti,Fe)
 
8
O
 
16
4.DK.05Redledgeite
Ba
 
x
([Cr,Fe,V]
3+
2x
Ti
 
8-2x
)O
 
16
4.DK.05Henrymeyerite
BaFe
2+
 
Ti
 
7
O
 
16
4.DK.10Romanèchite
(Ba,H
 
2
O)
 
2
Mn
 
5
O
 
10
4.DK.10Todorokite
(Ca,K,Na,Mg,Ba,Mn)(Mn,Mg,Al)
 
6
O
 
12
·3H
 
2
O
4.DK.10Strontiomelane
SrMn
4+
6
Mn
3+
2
O
 
16
Related Minerals - Hey's Index Grouping:

- +
7.2.1Lithiophorite
(Al,Li)MnO
 
2
(OH)
 
2
7.2.2Diaoyudaoite
NaAl
 
11
O
 
17
7.2.3Manjiroite
(Na,K)Mn
 
8
O
 
16
·nH
 
2
O

Other Names for Cryptomelane

Synonyms:
EbelmeniteIMA1982-s.p.
Other Languages:
German:Barium-Kalium-Psilomelan
Ebelmenit
Kryptomelan
Italian:Criptomelano
Russian:Криптомелан
Spanish:Ebelmenita
Varieties:
Thallian Cryptomelane

Other Information

Health Warning: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

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  • Look for Cryptomelane on Wikipedia
  • Look for Cryptomelane on Mineralien Atlas
  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Cryptomelane in the Natural History Museum (London) online catalogue
  • Cryptomelane details from Handbook of Mineralogy (PDF)
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    Localities for Cryptomelane

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