Mineralogy Database

Cryptomelane Mineral Data

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General Cryptomelane Information

Help on Chemical  Formula: Chemical Formula: K(Mn++++,Mn++)8O16
Help on Composition: Composition: Molecular Weight = 734.59 gm
   Potassium   5.32 %  K     6.41 % K2O
   Manganese  59.83 %  Mn   19.31 % MnO / 71.01 % MnO2
   Oxygen     34.85 %  O
             ______        ______ 
             100.00 %       96.73 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: KMn4+6Mn2+2O16
Help on Environment: Environment: Commonest of the hard, black, fine-grained manganese oxides formerly called psilomelane.
Help on IMA Status: IMA Status: Valid Species (Pre-IMA) 1942
Help on Locality: Locality: Chindwara, India. Link to MinDat.org Location Data.
Help on Name Origin: 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.
Help on Name Pronunciation: Name Pronunciation: Cryptomelane + Pronunciation Say CRYPTOMELANE
Help on Synonym: Synonym: Psilomelane

Cryptomelane Image

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  Cryptomelane   Adamite

Comments: Black, rounded balls of cryptomelane and purple, transparent adamite.
Location: Ojuela mine, Mapimi, Druango, Mexico. Scale: Not Given.
© Lou Perloff / Photo Atlas of Minerals

Cryptomelane Crystallography

Help on Axial Ratios: Axial Ratios: a:b:c =3.3993:1:3.4513
Help on Cell Dimensions: Cell Dimensions: a = 9.79, b = 2.88, c = 9.94, Z = 1; beta = 90.62° V = 280.24 Den(Calc)= 4.35
Help on Crystal System: Crystal System: Monoclinic - Prismatic H-M Symbol (2/m) Space Group: I2/m
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 2.399(1), 1.654(0.8), 3.11(0.8),

Physical Properties of Cryptomelane

Help on Color: Color: Black, Gray, Blue gray.
Help on Density: Density: 4.36
Help on Diaphaneity: Diaphaneity: Opaque
Help on Fracture: Fracture: Conchoidal - Fractures developed in brittle materials characterized by smoothly curving surfaces, (e.g. quartz).
Help on Habit: Habit: Botryoidal - "Grape-like" rounded forms (e.g.. malachite).
Help on Habit: Habit: Cryptocrystalline - Occurs as crystals too small to distinguish with the naked eye.
Help on Habit: Habit: Massive - Uniformly indistinguishable crystals forming large masses.
Help on Hardness: Hardness: 6-6.5 - Orthoclase-Pyrite
Help on Luster: Luster: Sub Metallic
Help on Streak: Streak: brownish black

Optical Properties of Cryptomelane

Help on Optical Data: 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

Calculated Properties of Cryptomelane

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=4.11 gm/cc
note: Specific Gravity of Cryptomelane =4.35 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.0001736569
Boson Index = 0.9998263431
Help on Photoelectric: Photoelectric: PECryptomelane = 16.25 barns/electron
U=PECryptomelane x relectron= 66.76 barns/cc.
Help on Radioactivity: Radioactivity:

GRapi = 72.57 (Gamma Ray American Petroleum Institute Units)
Concentration of Cryptomelane per GRapi unit = 1.38 (%)

Estimated Radioactivity from Cryptomelane - barely detectable


Cryptomelane Classification

Help on  Dana Class: Dana Class: (07)Multiple Oxides
  (07.09)Dana Type
  (07.09.01)Cryptomelane Group (Hard black, fine-grained) Hollandite Ba(Mn,Mn)8O16 I2/m 2/m Cryptomelane K(Mn,Mn)8O16 I2/m 2/m Manjiroite (Na,K)(Mn,Mn)8O16•n(H2O) I 4/m 4/m Coronadite Pb(Mn,Mn)8O16 I2/m 2/m Strontiomelane! SrMn6Mn2O16 P 21/m 2/m Henrymeyerite! BaFeTi7O16 I 4/m 4/m
Help on  Strunz Class: Strunz Class: 04.DK.10 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate
  04.D - Metal:Oxygen = 1:2 and similar
  04.DK -With large (� medium-sized) cations; tunnel structures
04.DK.10 Cryptomelane K(Mn,Mn)8O16 I2/m 2/m
04.DK.10 Todorokite (Na,Ca,K)2(Mn,Mn)6O12•3-4.5(H2O) P 2/m 2/m
04.DK.10 Romanechite (Ba,H2O)2(Mn,Mn)5O10 C 2/m 2/m
04.DK.10 Strontiomelane! SrMn6Mn2O16 P 21/m 2/m

Other Cryptomelane Information

Help on References: References: NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990)
Help on See Also: 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
16 - theimage

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Dana No: Strunz No: 04.DK.10





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