Cryptomelane Mineral Data

Cryptomelane Mineral Data +

General Cryptomelane Information

Chemical Formula:

K(Mn++++,Mn++)8O16

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

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.

Synonym:

Psilomelane

Cryptomelane Image

Images:

Click Here for Larger Cryptomelane Image

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

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 - PrismaticH-M Symbol (2/m) Space Group: I2/m

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.399(1), 1.654(0.8), 3.11(0.8),

Crystal Structure:

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Post J E , Von Dreele R B , Buseck P R , Acta Crystallographica, Section B , 38 (1982) p.1056-1065, Symmetry and cation displacements in hollandites:, structure refinements of hollandite, cryptomelane and priderite, Locality: Chindwara, India, Note: -1M polytype, Note: Anisotropic displacement factors from ICSD

Physical Properties of Cryptomelane

Color:

Black, Gray, Blue gray.

Density:

4.36

Diaphaniety:

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

Calculated Properties of Cryptomelane

Electron Density:

r_electron=4.11 gm/cc
note: r_Cryptomelane=4.35 gm/cc.

Fermion Index

Fermion Index = 0.00017
Boson Index = 0.99983

Photoelectric:

PE_Cryptomelane= 16.25 barns/electron
U=PE_Cryptomelane x r_electron= 66.76 barns/cc.

Radioactivity:

GRapi = 72.57 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Cryptomelane - barely detectable

Cryptomelane Classification

Dana Class:

7.9.1.2 (7)Multiple Oxides

(7.9)where A B (O)2

(7.9.1)Cryptomelane Group (Hard black, fine-grained)

7.9.1.1 Hollandite Ba(Mn,Mn)8O16 I2/m 2/m

7.9.1.2 Cryptomelane K(Mn,Mn)8O16 I2/m 2/m

7.9.1.3 Manjiroite (Na,K)(Mn,Mn)8O16·n(H2O) I 4/m 4/m

7.9.1.4 Coronadite Pb(Mn,Mn)8O16 I2/m 2/m

7.9.1.5 Strontiomelane! SrMn6Mn2O16 P 2₁/m 2/m

7.9.1.6 Henrymeyerite! BaFeTi7O16 I 4/m 4/m

Strunz Class:

IV/D.08-20 IV - Oxides

IV/D - Oxides with metal : oxygen = 1:2 (MO2 and related compounds)

IV/D.08 - Cryptomelane group

IV/D.08-10 Manjiroite (Na,K)(Mn,Mn)8O16·n(H2O) I 4/m 4/m

IV/D.08-20 Cryptomelane K(Mn,Mn)8O16 I2/m 2/m

IV/D.08-25 Strontiomelane! SrMn6Mn2O16 P 2₁/m 2/m

IV/D.08-30 Priderite (K,Ba)(Ti,Fe)8O16 I 4/m 4/m

IV/D.08-33 Henrymeyerite! BaFeTi7O16 I 4/m 4/m

IV/D.08-35 Ankangite Ba(Ti,V,Cr)8O16 I 4/m 4/m

IV/D.08-40 Mannardite BaTi6V2O16·(H2O) I 4₁/a 4/m

IV/D.08-50 Redledgeite BaTi6Cr2O16·(H2O) I 4₁/a 4/m

IV/D.08-60 Hollandite Ba(Mn,Mn)8O16 I2/m 2/m

IV/D.08-70 Coronadite Pb(Mn,Mn)8O16 I2/m 2/m

IV/D.08-80 Cesarolite PbH2Mn3O8 HEX-R Trig

Other Cryptomelane Information

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990)

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Cryptomelane

K(Mn++++,Mn++)8O16
Dana No: 7.9.1.2 Strunz No: IV/D.08-20
Locality:

Notes: