Coombsite
A valid IMA mineral species
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About Coombsite
Formula:
KMn2+13(Si,Al)18O42(OH)14
Type material has Si:Al = 16.41:1.54.
Colour:
Pale brownish yellow
Specific Gravity:
3.0
Crystal System:
Trigonal
Name:
Named in 1991 by Teruhiko Sameshima and Yosuke Kawachi in honor of Douglas S. Coombs (23 November 1924 – 23 December 2016), professor of geology at the University of Otago, New Zealand. Coombs first described progressive mineralogical changes, especially relating to zeolites, due to low grade burial metamorphism. Coombs named wairakite, ferroceladonite, and ferroaluminoceladonite.
Type Locality:
Isostructural with:
Mn-analogue of zussmanite.
Compare the chemically and stoichiometrically very similar franklinphilite.
Compare also the chemically similar ganophyllite and parsettensite.
Compare the chemically and stoichiometrically very similar franklinphilite.
Compare also the chemically similar ganophyllite and parsettensite.
Unique Identifiers
Mindat ID:
1122
Long-form identifier:
mindat:1:1:1122:4
IMA Classification of Coombsite
Classification of Coombsite
9.EG.35
9 : SILICATES (Germanates)
E : Phyllosilicates
G : Double nets with 6-membered and larger rings
9 : SILICATES (Germanates)
E : Phyllosilicates
G : Double nets with 6-membered and larger rings
16.16.18
16 : Silicates Containing Aluminum and other Metals
16 : Aluminosilicates of Mn
16 : Silicates Containing Aluminum and other Metals
16 : Aluminosilicates of Mn
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 |
|---|---|---|
| Cmb | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Cmb | 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 Coombsite
Transparency:
Translucent
Colour:
Pale brownish yellow
Density:
3.0(1) g/cm3 (Measured) 3.063 g/cm3 (Calculated)
Optical Data of Coombsite
Type:
Uniaxial (-)
RI values:
nω = 1.619(1) nε = 1.600(1)
Max. Birefringence:
δ = 0.019
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized uniaxial interference figure - the conoscopic
(convergent-light, Bertrand-lens-in) view, for a grain cut with the optic axis
centred and vertical. The coloured rings are isochromatics, computed with the
same physics as the Michel-Lévy bar above; the dark cross is the isogyre.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
For a genuinely uniaxial mineral viewed this way, that cross stays perfectly stationary if you rotate the stage - unlike a biaxial mineral, where it splits apart on rotation. That invariance is itself the standard diagnostic test for telling uniaxial and biaxial minerals apart at the microscope.
Optical Extinction:
Parallel extinction, length slow.
Pleochroism:
Weak
Comments:
First-order red to purple interference colours in standard thin sections.
Chemistry of Coombsite
Mindat Formula:
KMn2+13(Si,Al)18O42(OH)14
Type material has Si:Al = 16.41:1.54.
Type material has Si:Al = 16.41:1.54.
Element Weights:
Common Impurities:
Ti,Ca,Na
Crystallography of Coombsite
Crystal System:
Trigonal
Cell Parameters:
a = 11.82 Å, c = 29.14 Å
Ratio:
a:c = 1 : 2.465
Unit Cell V:
3,525.78 ų (Calculated from Unit Cell)
Comment:
Space group R3 or R-3.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.68 Å | (100) |
| 4.835 Å | (30) |
| 3.241 Å | (25) |
| 2.793 Å | (70) |
| 2.556 Å | (90) |
| 2.241 Å | (50) |
Comments:
Very similar to the data of zussmanite.
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 5: Initiation of plate tectonics | <3.5-2.5 |
| 40 : Regional metamorphism (greenschist, amphibolite, granulite facies) |
Type Occurrence of Coombsite
General Appearance of Type Material:
Aggregates of fibro-lamellar crystals up to 20 micron in length, and often shows semispherulitic texture.
Place of Conservation of Type Material:
The type material (OU34460) is deposited in the Museum of the Geology Department, University of Otago, and Smithsonian Institution, Washington, D.C., U.S.A.
Geological Setting of Type Material:
A 50 cm thick rhodonite-quartz lens.
Associated Minerals at Type Locality:
Synonyms of Coombsite
Other Language Names for Coombsite
Common Associates
Associations Based on Photo Data:
Related Minerals - Strunz-mindat Grouping
| 9.EG.05 | Cymrite | BaAl2Si2(O,OH)8 · H2O |
| 9.EG.10 | Naujakasite | (Na,K)6(Fe2+,Mn2+,Ca)(Al,Fe)4Si8O26 |
| 9.EG.10 | Manganonaujakasite | Na6(Mn2+,Fe2+)Al4Si8O26 |
| 9.EG.15 | Dmisteinbergite | Ca(Al2Si2O8) |
| 9.EG.20 | Kampfite | Ba12(Si11Al5)O31(CO3)8Cl5 |
| 9.EG.25 | Vertumnite | Ca4Al4Si4O6(OH)24 · 3H2O |
| 9.EG.25 | Strätlingite | Ca2Al2SiO7 · 8H2O |
| 9.EG.30 | Eggletonite | (Na,K,Ca)xMn6(Si,Al)10O24(OH)4 · nH2O (x = 1-2; n = 7-11) |
| 9.EG.30 | Ganophyllite | (K,Na)xMn2+6(Si,Al)10O24(OH)4 · nH2O (x = 1-2; n = 7-11) |
| 9.EG.30 | Tamaite | (Ca,K,Na)xMn6(Si,Al)10O24(OH)4 · nH2O (x = 1-2; n = 7-11) |
| 9.EG.35 | Zussmanite | K(Fe,Mg,Mn)13(Si,Al)18O42(OH)14 |
| 9.EG.40 | 'Chalcodite' | K(Fe3+,Mg,Fe2+)8(Si,Al)12(O,OH)27 |
| 9.EG.40 | Parsettensite | (K,Na,Ca)7.5(Mn,Mg)49Si72O168(OH)50 · nH2O |
| 9.EG.40 | Lennilenapeite | K4Mn2+48[Si64Al8]O164(OH)52 · nH2O |
| 9.EG.40 | Stilpnomelane | K4Fe2+48[Si64Al8]O164(OH)52 · nH2O |
| 9.EG.45 | Latiumite | (Ca,K)4(Si,Al)5O11(SO4,CO3) |
| 9.EG.45 | Levantite | KCa3Al2(SiO4)(Si2O7)(PO4) |
| 9.EG.45 | Tuscanite | KCa6(Si,Al)10O22(SO4,CO3)2(OH) · H2O |
| 9.EG.50 | Jagoite | Pb18Fe3+4[Si4(Si,Fe3+)6][Pb4Si16(Si,Fe)4]O82Cl6 |
| 9.EG.50 | Friisite | Pb8Al3Si8O27Cl3 |
| 9.EG.55 | Wickenburgite | CaPb3Al2Si10O24(OH)6 |
| 9.EG.60 | Hyttsjöite | Pb18Ba2Ca5Mn2+2Fe3+2Si30O90Cl · 6H2O |
| 9.EG.65 | Armbrusterite | K5Na7Mn15[(Si9O22)4](OH)10 · 4H2O |
| 9.EG.70 | Roymillerite | Pb24Mg9(Si10O28)(CO3)10(BO3)(SiO4)(OH)13O5 |
| 9.EG.70 | Britvinite | [Pb7(OH)3F(BO3)2(CO3)][Mg4.5(OH)3(Si5O14)] |
| 9.EG.75 | Kayupovaite | Na2Mn10[(Si14Al2)O38(OH)8] · 7H2O |
| 9.EG.75 | 'UM1989-30-SiO:AlBaCaFeHKMgMn' | (Ba,Ca)(Mn,Fe,Mg)22(Si,Al)32O76(OH)16 · 12H2O |
| 9.EG.75 | Bannisterite | (Ca,K,Na)(Mn2+,Fe2+)10(Si,Al)16O38(OH)8 · nH2O |
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) | 1.8027% | 559 | 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
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 Coombsite
mindat.org URL:
https://www.mindat.org/min-1122.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Coombsite
Localities for Coombsite
Showing 6 localities.
symbol to view information about a locality.
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.
Austria | |
| Kolitsch et al. (2021) |
Brazil | |
| Färber (n.d.) |
New Zealand (TL) | |
| Sameshima et al. (1991) |
Romania | |
| minerals-of-the-carpathians.eu (2008) |
Russia | |
| Semkova +3 other references |
| Старикова (2011) |
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Watsons Beach, Clutha District, Otago Region, New Zealand