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Cryptomelane Mineral Data
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General Cryptomelane Information
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 Chemical Formula: |
K(Mn++++,Mn++)8O16 |
| Composition: |
Molecular Weight = 734.59 gm |
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Potassium 5.32 % K 6.41 % K2O |
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Manganese 59.83 % Mn 19.31 % MnO / 71.01 % MnO2 |
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Oxygen 34.85 % O |
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______ ______ |
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100.00 % 96.73 % = TOTAL OXIDE |
| Empirical Formula: |
KMn4+6Mn2+2O16 |
| Environment: |
Commonest of the hard, black, fine-grained manganese oxides formerly called psilomelane. |
| IMA Status: |
Valid Species (Pre-IMA) 1942 |
| Locality: |
Chindwara, India. Link to MinDat.org Location Data. |
| Name Origin: |
From the Greek for hidden and black, as the identity of this common, black mineral is lost in the group of other black Mn-bearing oxides. |
| Name Pronunciation: |
Cryptomelane + Pronunciation  |
| Synonym: |
Psilomelane |
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Cryptomelane Image |
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Images:
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Cryptomelane Crystallography
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| Axial Ratios: |
a:b:c =3.3993:1:3.4513 |
| Cell Dimensions: |
a = 9.79, b = 2.88, c = 9.94, Z = 1; beta = 90.62° V = 280.24 Den(Calc)= 4.35 |
| Crystal System: |
Monoclinic - Prismatic H-M Symbol (2/m) Space Group: I2/m |
| X Ray Diffraction: |
By Intensity(I/Io): 2.399(1), 1.654(0.8), 3.11(0.8), |
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Physical Properties of Cryptomelane
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| Color: |
Black, Gray, Blue gray. |
| Density: |
4.36 |
| Diaphaneity: |
Opaque |
| Fracture: |
Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz). |
| Habit: |
Botryoidal - "Grape-like" rounded forms (e.g.. malachite). |
| Habit: |
Cryptocrystalline - Occurs as crystals too small to distinguish with the naked eye. |
| Habit: |
Massive - Uniformly indistinguishable crystals forming large masses. |
| Hardness: |
6-6.5 - Orthoclase-Pyrite |
| Luster: |
Sub Metallic |
| Streak: |
brownish black |
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Optical Properties of Cryptomelane
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| Optical Data: |
NCalc= 2.44 - from Gladstone-Dale relationship (KC = 0.3304) where Ncalc=Dcalc*KC+1
NCalc= 2.44 - from Gladstone-Dale relationship (KC = 0.3304) where Ncalc=Dmeas*KC+1
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Calculated Properties of Cryptomelane
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| Electron Density: |
Bulk Density (Electron Density)=4.11 gm/cc
note: Specific Gravity of Cryptomelane =4.35 gm/cc.
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| Fermion Index: |
Fermion Index = 0.0001736569
Boson Index = 0.9998263431 |
| Photoelectric: |
PECryptomelane = 16.25 barns/electron
U=PECryptomelane x relectron= 66.76 barns/cc.
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| Radioactivity: |
GRapi = 72.57 (Gamma Ray American Petroleum Institute Units)
Concentration of Cryptomelane per GRapi unit = 1.38 (%)
Estimated Radioactivity from Cryptomelane  - barely detectable
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Cryptomelane Classification
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| Dana Class: |
07.09.01.02 (07)Multiple Oxides |
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(07.09)Dana Type |
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(07.09.01)Cryptomelane Group (Hard black, fine-grained) |
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07.09.01.01 Hollandite Ba(Mn,Mn)8O16 I2/m 2/m |
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07.09.01.02 Cryptomelane K(Mn,Mn)8O16 I2/m 2/m |
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07.09.01.03 Manjiroite (Na,K)(Mn,Mn)8O16•n(H2O) I 4/m 4/m |
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07.09.01.04 Coronadite Pb(Mn,Mn)8O16 I2/m 2/m |
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07.09.01.05 Strontiomelane! SrMn6Mn2O16 P 21/m 2/m |
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07.09.01.06 Henrymeyerite! BaFeTi7O16 I 4/m 4/m |
| Strunz Class: |
04.DK.10 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate |
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04.D - Metal:Oxygen = 1:2 and similar |
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04.DK -With large (� medium-sized) cations; tunnel structures |
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04.DK.10 Cryptomelane K(Mn,Mn)8O16 I2/m 2/m |
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04.DK.10 Todorokite (Na,Ca,K)2(Mn,Mn)6O12•3-4.5(H2O) P 2/m 2/m |
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04.DK.10 Romanechite (Ba,H2O)2(Mn,Mn)5O10 C 2/m 2/m |
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04.DK.10 Strontiomelane! SrMn6Mn2O16 P 21/m 2/m |
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Other Cryptomelane Information
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| References: |
NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) |
| See Also: |
Links to other databases for Cryptomelane :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - Ecole des Mines de Paris
4 - Franklin Minerals(Dunn)
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
16 - theimage
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Print or Cut-and-Paste your Cryptomelane Specimen Label here :
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Cryptomelane
K(Mn++++,Mn++)8O16
Dana No: 07.09.01.02 Strunz No: 04.DK.10
Locality:
Notes:
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