Cryptomelane
A valid IMA mineral species - grandfathered
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About Cryptomelane
Formula:
K(Mn4+7Mn3+)O16
Colour:
Brown, grayish-white
Lustre:
Resinous, Dull, Earthy
Hardness:
5 - 6½
Specific Gravity:
4.17 - 4.41
Crystal System:
Monoclinic
Member of:
Name:
Named in 1942 by Wallace E. Richmond and Forrest A. Gonyer From the Greek words meaning κρυπτοζ "hidden" and μέλας "black," since the identity of this common black manganese mineral had been hidden within a group of manganese oxides.
Isostructural with:
Visually indistinguishable from hollandite and several other manganese oxide minerals.
Many manganese oxides are better identified using infra-red spectroscopy than by X-ray diffraction because of issues of crystal size, disorder, etc. (Potter and Rossman, 1979).
Many manganese oxides are better identified using infra-red spectroscopy than by X-ray diffraction because of issues of crystal size, disorder, etc. (Potter and Rossman, 1979).
Unique Identifiers
Mindat ID:
1164
Long-form identifier:
mindat:1:1:1164:4
IMA Classification of Cryptomelane
Approved, 'Grandfathered' (first described prior to 1959)
Approval year:
1982
Classification of Cryptomelane
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
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 : MULTIPLE OXIDES
9 : AB8X16
7.2.4
7 : Oxides and Hydroxides
2 : Oxides of the alkali metals
7 : Oxides and Hydroxides
2 : Oxides of the alkali metals
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Cml | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Cpt | The Canadian Mineralogist (2019) | The Canadian Mineralogist (2019) The Canadian Mineralogist list of symbols for rock- and ore-forming minerals (December 30, 2019). download |
| Cml | Warr (2020) | Warr, L.N. (2020) Recommended abbreviations for the names of clay minerals and associated phases. Clay Minerals, 55, 261–264 doi:10.1180/clm.2020.30 |
Physical Properties of Cryptomelane
Resinous, Dull, Earthy
Transparency:
Opaque
Colour:
Brown, grayish-white
Streak:
Brownish black
Hardness:
5 - 6½ on Mohs scale
Tenacity:
Brittle
Density:
4.17 - 4.41 g/cm3 (Measured) 4.44 g/cm3 (Calculated)
Chemistry of Cryptomelane
Mindat Formula:
K(Mn4+7Mn3+)O16
Elements listed:
Chemical Analysis
Oxide wt%:
| 1 | |
|---|---|
| Mn2O3 | 81.0 % |
| Fe2O3 | 0.8 % |
| Al2O3 | 0.5 % |
| K2O | 3.3 % |
| Na2O | 0.8 % |
| H2O | 12.2 % |
| Total: | 98.6 % |
Sample references:
| ID | Locality | Reference | Notes |
|---|---|---|---|
| 1 | Lierneux, Liège, Wallonia, Belgium | Analysis by Pisani |
Crystallography of Cryptomelane
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 9.956 Å, b = 2.8705 Å, c = 9.706 Å
β = 90.95°
β = 90.95°
Ratio:
a:b:c = 3.468 : 1 : 3.381
Unit Cell V:
277.35 ų (Calculated from Unit Cell)
Z:
1
Comment:
Non-standard I2/m setting; pseudo-tetragonal
Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0016237 | Cryptomelane | Vicat J, Fanchon E, Strobel P, Tran Qui D (1986) The structure of K1.33Mn8O16 and cation ordering in hollandite-type structures _cod_database_code 1008322 Acta Crystallographica B42 162-167 |  | 1986 | synthetic | 0 | 293 |
| 0009758 | Cryptomelane | Post J E, Von Dreele R B, Buseck P R (1982) Symmetry and cation displacements in hollandites: structure refinements of hollandite, cryptomelane and priderite Acta Crystallographica B38 1056-1065 | | 1982 | Chindwara, India | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Loading XRD data...
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.90 Å | (90) |
| 4.90 Å | (80) |
| 3.45 Å | (10) |
| 3.10 Å | (80) |
| 2.46 Å | (10) |
| 2.39 Å | (100) |
| 2.19 Å | (20) |
| 2.15 Å | (60) |
| 1.92 Å | (10) |
| 1.83 Å | (60) |
| 1.64 Å | (30) |
| 1.54 Å | (60) |
| 1.42 Å | (40) |
| 1.35 Å | (50) |
| 1.29 Å | (20) |
Comments:
ICDD 20-908 (Tetragonal; Phillipsburg, Montana, USA). Very similar to coronadite. ICDD 34-168 (Monoclinic; Chindwara, India; calculated): 7.007 (79), 6.892 (82), 4.977 (72), 4.852 (91), 3.504 (15), 3.446 (15), 3.156 (43), 3.124 (99), 3.092 (100), 3.062 (44), 2.753 (3), 2.489 (25), 2.426 (22), 2.414 (54), 2.404 (99), 2.393 (77), 2.336 (10), 2.297 (6), 2.229 (5), 2.195 (20), 2.171 (36), 2.147 (33), 1.9897 (5), 1.9636 (4), 1.9567 (7), 1.9440 (3), 1.9110 (5), 1.8991 (2), 1.8504 (24), 1.8417 (22), 1.8258 (19), 1.8175 (32), 1.7518 (3), 1.7230 (3), 1.6876 (3), 1.6831 (3),1.6591 (24), 1.6360 (3), 1.6266 (3), 1.6174 (25), 1.6092 (15), 1.6079 (4), 1.5779 (3), 1.5567 (14), 1.5439 (32), 1.5362 (28), 1.5308 (17), 1.5239 (15), 1.4353 (19), 1.4239 (5)
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits | |
| Stage 7: Great Oxidation Event | <2.4 |
| 47e : [Vanadates, chromates, manganates] | |
| 47h : [Near-surface oxidized, dehydrated minerals] |
Type Occurrence of Cryptomelane
Synonyms of Cryptomelane
Other Language Names for Cryptomelane
Varieties of Cryptomelane
| Thallium-bearing Cryptomelane | A thallium-bearing cryptomelane (0.23 at% Tl). Compare thalliomelane. Originally reported from Peach Springs District, Coconino Co., Arizona, USA. |
Relationship of Cryptomelane to other Species
Member of:
Other Members of Coronadite Group:
| Coronadite | Pb(Mn4+6Mn3+2)O16 | Mon. 2/m |
| Ferricoronadite | Pb(Mn4+6Fe3+2)O16 | Tet. 4/m : I4/m |
| Ferrihollandite | Ba(Mn4+6Fe3+2)O16 | Mon. 2/m |
| Hollandite | Ba(Mn4+6Mn3+2)O16 | Mon. 2/m |
| Manjiroite | Na(Mn4+7Mn3+)O16 | Tet. 4/m : I4/m |
| Strontiomelane | Sr(Mn4+6Mn3+2)O16 | Mon. 2/m : P21/b |
| Thalliomelane | Tl(Mn4+7.5Cu2+0.5)O16 | Tet. 4/m : I4/m |
Common Associates
Associations Based on Photo Data:
| 91 photos of Cryptomelane associated with Goethite | Fe3+O(OH) |
| 48 photos of Cryptomelane associated with Lepidocrocite | Fe3+O(OH) |
| 34 photos of Cryptomelane associated with Pyrolusite | Mn4+O2 |
| 31 photos of Cryptomelane associated with Hollandite | Ba(Mn4+6Mn3+2)O16 |
| 27 photos of Cryptomelane associated with Scholzite | CaZn2(PO4)2 · 2H2O |
| 25 photos of Cryptomelane associated with Malachite | Cu2(CO3)(OH)2 |
| 24 photos of Cryptomelane associated with Azurite | Cu3(CO3)2(OH)2 |
| 17 photos of Cryptomelane associated with 'Wad' | |
| 17 photos of Cryptomelane associated with Quartz | SiO2 |
| 13 photos of Cryptomelane associated with Aurorite | Mn2+Mn4+3O7 · 3H2O |
Related Minerals - Strunz-mindat Grouping
| 4.DK.K | Thalliomelane | Tl(Mn4+7.5Cu2+0.5)O16 |
| 4.DK. | Ferrihollandite | Ba(Mn4+6Fe3+2)O16 |
| 4.DK. | Kopernikite | K(Ti7Cr3+)O16 |
| 4.DK.4.DK. | Ferricoronadite | Pb(Mn4+6Fe3+2)O16 |
| 4.DK.05a | Manjiroite | Na(Mn4+7Mn3+)O16 |
| 4.DK.05b | Mannardite | Ba(Ti4+6V3+2)O16 |
| 4.DK.05b | Redledgeite | Ba(Ti4+6Cr3+2)O16 |
| 4.DK.05 | Akaganeite | (Fe3+,Ni2+)8(OH,O)16Cl1.25 · nH2O |
| 4.DK.05a | Coronadite | Pb(Mn4+6Mn3+2)O16 |
| 4.DK.05a | Hollandite | Ba(Mn4+6Mn3+2)O16 |
| 4.DK.05a | Strontiomelane | Sr(Mn4+6Mn3+2)O16 |
| 4.DK.05b | Henrymeyerite | Ba(Ti4+7Fe2+)O16 |
| 4.DK.05b | Priderite | K(Ti4+7Fe3+)O16 |
| 4.DK.10 | Romanèchite | (Ba,H2O)2(Mn4+,Mn3+)5O10 |
| 4.DK.10 | Todorokite | (Na,Ca,K,Ba,Sr)1-x(Mn,Mg,Al)6O12 · 3-4H2O |
Radioactivity
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, β, γ |
| Thorium (Th) | 0.0000% | 0 | α, β, γ |
| Potassium (K) | 5.3224% | 1,650 | β, γ |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000–3,000 Bq/kg
- EU exemption limit: 10,000 Bq/kg
Note: Risk is shown relative to daily recommended maximum exposure to non-background radiation of 1000 µSv/year. Note that natural background radiation averages around 2400 µSv/year so in reality these risks are probably extremely overstated! With infrequent handling and safe storage natural radioactive minerals do not usually pose much risk.
Interactive Simulator:
Note: The mass selector refers to the mass of radioactive mineral present, not the full specimen, also be aware that the matrix may also be radioactive, possibly more radioactive than this mineral!
Activity: –
| Distance | Dose rate | Risk |
|---|---|---|
| 1 cm | ||
| 10 cm | ||
| 1 m |
The external dose rate (D) from a radioactive mineral is estimated by summing the gamma radiation contributions from its Uranium, Thorium, and Potassium content, disregarding daughter-product which may have a significant effect in some cases (eg 'pitchblende'). This involves multiplying the activity (A, in Bq) of each element by its specific gamma ray constant (Γ), which accounts for its unique gamma emissions. The total unshielded dose at 1 cm is then scaled by the square of the distance (r, in cm) and multiplied by a shielding factor (μshield). This calculation provides a 'worst-case' or 'maximum risk' estimate because it assumes the sample is a point source and entirely neglects any self-shielding where radiation is absorbed within the mineral itself, meaning actual doses will typically be lower. The resulting dose rate (D) is expressed in microsieverts per hour (μSv/h).
D = ((AU × ΓU) + (ATh × ΓTh) + (AK × ΓK)) / r2 × μshield
Fluorescence of Cryptomelane
Not fluorescent in ultraviolet
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.
Internet Links for Cryptomelane
mindat.org URL:
https://www.mindat.org/min-1164.html
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References for Cryptomelane
Reference List:
Richmond, Wallace E., Fleischer, Michael (1942) Cryptomelane, a new name for the commonest of the "psilomelane" minerals. American Mineralogist, 27 (9) 607-610
Gruner, John W. (1943) The chemical relationship of cryptomelane (psilomelane), hollandite, and coronadite. American Mineralogist, 28 (9-10) 497-506
Mukherjee, Bibhuti (1959) X-ray study of psilomelane and cryptomelane. Mineralogical Magazine and Journal of the Mineralogical Society, 32 (245) 166-171 doi:10.1180/minmag.1959.32.245.08
Larson, Lawrence T. (1964) Geology and mineralogy of certain manganese oxide deposits. Economic Geology, 59 (1) 54-78 doi:10.2113/gsecongeo.59.1.54
Hewett, D. F., Olivares, Raul Salas (1968) High-potassium cryptomelane from Tarapaca Province, Chile. American Mineralogist, 53 (9-10) 1551-1557
Ramdohr, Paul (1969) The Ore Minerals and their Intergrowths. Pergamon Press, Oxford. 1174pp. doi:10.1016/c2013-0-10027-x
Hewett, D. F., Olivares, Raul Salas (1969) High-potassium cryptomelane from Tarapaca Province, Chile: Errata. American Mineralogist, 54 (3-4) 572
Perseil, E. A.; Pinet, M. (1976) Contribution à la connaissance des romanèchites et des cryptomélanes - coronadites - hollandites. Traits essentiels et paragenèses. Contributions to Mineralogy and Petrology, 55 (2). 191-204 doi:10.1007/bf00372226
Potter, Russell M., Rossman, George R (1979) The tetravalent manganese oxides: identification, hydration, and structural relationships by infrared spectroscopy. American Mineralogist, 64 (11-12) 1199-1218
Nambu, Matsuo, Tanida, Katsutoshi (1980) Cryptomelane-Manjiroite-Hollandite Series Minerals. Journal of the Mineralogical Society of Japan, 14. 62-85 doi:10.2465/gkk1952.14.special3_62
Post, J. E., Von Dreele, R. B., Buseck, P. R. (1982) Symmetry and cation displacements in hollandites: structure refinements of hollandite, cryptomelane and priderite. Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry, 38 (4) 1056-1065 doi:10.1107/s0567740882004968
Localities for Cryptomelane
Showing 758 localities.
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The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
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Salisbury Mine, Salisbury, Litchfield County, Connecticut, USA