Montdorite
About Montdorite
Unique Identifiers
IMA Classification of Montdorite
Classification of Montdorite
9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
71 : PHYLLOSILICATES Sheets of Six-Membered Rings
2 : Sheets of 6-membered rings with 2:1 layers
14 : Silicates not Containing Aluminum
20 : Silicates of Fe and alkali metals
Mineral Symbols
Please only use the official IMA–CNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Mdr | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Mdr | 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 Montdorite
Optical Data of Montdorite
Based on recorded range of RI values above.
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.
Relative to Canada balsam mounting medium (n ≈ 1.537).
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
No measured or calculated 2V is on file for this mineral, so the value used here (-0°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Chemistry of Montdorite
Crystallography of Montdorite
β = 99.9°
X-Ray Powder Diffraction
| d-spacing | Intensity |
|---|---|
| 9.97 Å | (43) |
| 3.41 Å | (35) |
| 3.339 Å | (100) |
| 3.142 Å | (26) |
| 2.710 Å | (34) |
| 2.519 Å | (39) |
| 2.172 Å | (25) |
| 1.669 Å | (31) |
Geological Environment
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 4a: Earth’s earliest continental crust | >4.4-3.0 |
| 20 : Acidic volcanic rocks | |
| High-? alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits |
Type Occurrence of Montdorite
Natural History Museum, London, United Kingdom, number BM 1983,43 (cotype).
National Museum of Natural History, Washington, D.C., USA, number 142228 or 2228 (type).
Other Language Names for Montdorite
Relationship of Montdorite to other Species
| Dioctahedral mica | A major subgroup of the micas, where there are two octahedrally coordinated D cations per formula unit. | |
| Trioctahedral mica | A major subgroup of the micas, where there are three octahedrally coordinated D cations per formula unit. | |
| 'UM1988-22-SiO:AlCaFFeHKLiMg' | KLiMgAl2Si3O10F2 | Mon. |
| 'UM2003-27-SiO:AlCsFFeHLi' | CsFe2+3(Si3Al)O10(F,OH)2 | |
| 'UM2003-28-SiO:AlCsFFeHMg' | Cs(Mg,Fe)3(Si3Al)O10(F,OH)2 | |
| 'UM2003-30-SiO:AlFLiRb' | RbLi2AlSi4O10(F,OH)2 | |
| 'UM2003-31-SiO:AlHFeRb' | RbFe2+3(Si3Al)O10(OH,F)2 | |
| 'Unnamed Nickel-rich Mica' | K0.5(Ni1.5 Al0.6 Cr0.4 Mg0.2 Fe0.1) (Si3.3 Al0.7)O10(OH)2 | |
| Voloshinite | Rb(LiAl1.5◻0.5)(Al0.5Si3.5)O10F2 | Mon. 2/m : B2/b |
| Yangzhumingite | KMg2.5(Si4O10)F2 | Mon. 2/m : B2/m |
Common Associates
| 1 photo of Montdorite associated with 'Comenditic rhyolite' |
Related Minerals - Strunz-mindat Grouping
| 9.EC. | Meifuite | KFe6(Si7Al)O19(OH)4Cl2 |
| 9.EC. | Balestraite | KLi2V5+Si4O12 |
| 9.EC.05 | Talc | Mg3Si4O10(OH)2 |
| 9.EC.05 | Minnesotaite | Fe2+3Si4O10(OH)2 |
| 9.EC.05 | Willemseite | Ni3Si4O10(OH)2 |
| 9.EC.9.EC. | Voloshinite | Rb(LiAl1.5◻0.5)(Al0.5Si3.5)O10F2 |
| 9.EC.10 | Fluorluanshiweiite | KLiAl1.5(Si3.5Al0.5)O10F2 |
| 9.EC.10 | Garmite | CsLiMg2(Si4O10)F2 |
| 9.EC.10 | Gorbunovite | CsLi2(Ti,Fe)Si4O10(F,OH,O)2 |
| 9.EC.10 | Ferripyrophyllite | Fe3+Si2O5(OH) |
| 9.EC.10 | Manganiceladonite | K(MgMn3+◻)(Si4O10)(OH)2 |
| 9.EC.10 | Luanshiweiite | KLiAl1.5(Si3.5Al0.5)O10(OH)2 |
| 9.EC.10 | Pyrophyllite | Al2Si4O10(OH)2 |
| 9.EC.15 | Paragonite | NaAl2(AlSi3O10)(OH)2 |
| 9.EC.15 | Ferroaluminoceladonite | K(Fe2+Al◻)(Si4O10)(OH)2 |
| 9.EC.15 | Nanpingite | CsAl2(AlSi3O10)(OH,F)2 |
| 9.EC.15 | Ferroceladonite | K(Fe2+Fe3+◻)(Si4O10)(OH)2 |
| 9.EC.15 | Ganterite | Ba0.5(Na,K)0.5Al2(Si2.5Al1.5)O10(OH)2 |
| 9.EC.15 | Kreiterite | CsLi2Fe3+(Si4O10)F2 |
| 9.EC.15 | Roscoelite | KV3+2(AlSi3O10)(OH)2 |
| 9.EC.15 | Aluminoceladonite | K(MgAl◻)(Si4O10)(OH)2 |
| 9.EC.15 | Tobelite | (NH4)Al2(AlSi3O10)(OH)2 |
| 9.EC.15 | Tainiolite | KLiMg2(Si4O10)F2 |
| 9.EC.15 | Celadonite | K(MgFe3+◻)(Si4O10)(OH)2 |
| 9.EC.15 | Chromceladonite | K(MgCr◻)(Si4O10)(OH)2 |
| 9.EC.15 | Chromphyllite | KCr2(AlSi3O10)(OH)2 |
| 9.EC.15 | Boromuscovite | KAl2(BSi3O10)(OH)2 |
| 9.EC.15 | 'UM1988-22-SiO:AlCaFFeHKLiMg' | KLiMgAl2Si3O10F2 |
| 9.EC.15 | Chernykhite | (Ba,Na)(V3+,Al,Mg)2((Si,Al)4O10)(OH)2 |
| 9.EC.15 | Muscovite | KAl2(AlSi3O10)(OH)2 |
| 9.EC.20 | Masutomilite | K(LiAlMn2+)[AlSi3O10]F2 |
| 9.EC.20 | Oxyphlogopite | K(Mg,Ti,Fe)3[(Si,Al)4O10](O,F)2 |
| 9.EC.20 | 'Chloroferrokinoshitalite' | (Ba,K)(Fe2+,Mg)3(Al2Si2O10)(Cl,OH,F)2 |
| 9.EC.20 | Siderophyllite | KFe2+2Al(Al2Si2O10)(OH)2 |
| 9.EC.20 | Sokolovaite | CsLi2Al(Si4O10)F2 |
| 9.EC.20 | Hendricksite | KZn3(Si3Al)O10(OH)2 |
| 9.EC.20 | Tetraferriphlogopite | KMg3(Si3Fe3+)O10(OH)2 |
| 9.EC.20 | Fluorannite | KFe2+3(Si3Al)O10F2 |
| 9.EC.20 | Aspidolite | NaMg3(AlSi3O10)(OH)2 |
| 9.EC.20 | Suhailite | (NH4)Fe2+3(AlSi3O10)(OH)2 |
| 9.EC.20 | Ephesite | NaLiAl2(Al2Si2O10)(OH)2 |
| 9.EC.20 | Norrishite | KLiMn3+2(Si4O10)O2 |
| 9.EC.20 | Phlogopite | KMg3(AlSi3O10)(OH)2 |
| 9.EC.20 | Yangzhumingite | KMg2.5(Si4O10)F2 |
| 9.EC.20 | Orlovite | KLi2Ti(Si4O10)OF |
| 9.EC.20 | Tetraferriannite | KFe2+3(Si3Fe3+)O10(OH)2 |
| 9.EC.20 | Shirokshinite | K(NaMg2)(Si4O10)F2 |
| 9.EC.20 | Trilithionite | K(Li1.5Al1.5)(AlSi3O10)(F,OH)2 |
| 9.EC.20 | Polylithionite | KLi2Al(Si4O10)(F,OH)2 |
| 9.EC.20 | Shirozulite | KMn2+3(Si3Al)O10(OH)2 |
| 9.EC.20 | Preiswerkite | NaMg2Al(Al2Si2O10)(OH)2 |
| 9.EC.20 | Fluorophlogopite | KMg3(Si3Al)O10F2 |
| 9.EC.20 | Wonesite | (Na,K,◻)(Mg,Fe,Al)6(Si,Al)8O20(OH,F)4 |
| 9.EC.20 | 'UM2004-49-SiO:AlCsFHKLi' | (Cs,K)(Al,Li)2.6((Si,Al)4O10)(F,OH)2 |
| 9.EC.20 | Fluorotetraferriphlogopite | KMg3(Fe3+Si3O10)F2 |
| 9.EC.20 | Annite | KFe2+3(AlSi3O10)(OH)2 |
| 9.EC.20 | Eastonite | KMg2Al(Al2Si2O10)(OH)2 |
| 9.EC.22 | 'Pimelite' | Ni3Si4O10(OH)2 · 4H2O |
| 9.EC.30 | Margarite | CaAl2(Al2Si2O10)(OH)2 |
| 9.EC.35 | Kinoshitalite | (Ba,K)(Mg,Mn2+,Al)3(Al2Si2O10)(OH)2 |
| 9.EC.35 | Ferrokinoshitalite | (Ba,K)(Fe2+,Mg)3(Al2Si2O10)(OH,F)2 |
| 9.EC.35 | Clintonite | CaAlMg2(SiAl3O10)(OH)2 |
| 9.EC.35 | Oxykinoshitalite | (Ba,K)(Mg,Ti,Fe3+,Fe2+)3((Si,Al)4O10)(O,OH,F)2 |
| 9.EC.35 | Fluorokinoshitalite | BaMg3(Al2Si2O10)F2 |
| 9.EC.35 | Bityite | CaLiAl2(AlBeSi2O10)(OH)2 |
| 9.EC.35 | Anandite | (Ba,K)(Fe2+,Mg)3((Si,Al,Fe)4O10)(S,OH)2 |
| 9.EC.40 | Montmorillonite | (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2 · nH2O |
| 9.EC.40 | Beidellite | (Na,Ca0.5)0.3Al2((Si,Al)4O10)(OH)2 · nH2O |
| 9.EC.40 | Volkonskoite | Ca0.3(Cr,Mg,Fe)2((Si,Al)4O10)(OH)2 · 4H2O |
| 9.EC.40 | Nontronite | Na0.3Fe2((Si,Al)4O10)(OH)2 · nH2O |
| 9.EC.40 | Kurumsakite | (Zn,Ni,Cu)8Al8V5+2Si5O35 · 27H2O (?) |
| 9.EC.40 | Yakhontovite | (Ca,Na)0.5(Cu,Fe,Mg)2(Si4O10)(OH)2 · 3H2O |
| 9.EC.45 | Swinefordite | Li(Al,Li,Mg)3((Si,Al)4O10)2(OH,F)4 · nH2O |
| 9.EC.45 | Hectorite | Na0.3(Mg,Li)3(Si4O10)(F,OH)2 |
| 9.EC.45 | Zincsilite | Zn3Si4O10(OH)2 · 4H2O (?) |
| 9.EC.45 | Hanjiangite | Ba2CaV3+Al(H2AlSi3O12)(CO3)2F |
| 9.EC.45 | Spadaite | MgSiO2(OH)2 · H2O (?) |
| 9.EC.45 | Ferrosaponite | Ca0.3(Fe2+,Mg,Fe3+)3((Si,Al)4O10)(OH)2 · 4H2O |
| 9.EC.45 | Stevensite | (Ca,Na)xMg3-x(Si4O10)(OH)2 |
| 9.EC.45 | Saponite | Ca0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O |
| 9.EC.45 | Sauconite | Na0.3Zn3((Si,Al)4O10)(OH)2 · 4H2O |
| 9.EC.50 | Vermiculite | Mg0.7(Mg,Fe,Al)6(Si,Al)8O20(OH)4 · 8H2O |
| 9.EC.52 | 'Tarasovite' | near NaKAl11Si13O40(OH)9 · 3H2O |
| 9.EC.55 | Clinochlore | Mg5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | Borocookeite | (LiAl4◻)[BSi3O10](OH)8 |
| 9.EC.55 | Franklinfurnaceite | Ca2Fe3+Mn2+3Mn3+(Zn2Si2O10)(OH)8 |
| 9.EC.55 | Pennantite | Mn2+5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | Vakhrushevaite | Mg5Cr(AlSi3O10)(OH)8 |
| 9.EC.55 | Nimite | Ni5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | Cookeite | (LiAl4◻)[AlSi3O10](OH)8 |
| 9.EC.55 | Gonyerite | Mn2+5Fe3+(Fe3+Si3O10)(OH)8 |
| 9.EC.55 | Chamosite | Fe2+5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | 'Orthochamosite' | (Fe2+,Mg,Fe3+)5Al(AlSi3O10)(OH,O)8 |
| 9.EC.55 | Baileychlore | Zn5Al(AlSi3O10)(OH)8 |
| 9.EC.55 | Sudoite | Mg2Al3(AlSi3O10)(OH)8 |
| 9.EC.55 | Glagolevite | Na(Mg,Al)6(AlSi3O10)(OH,O)8 |
| 9.EC.55 | Donbassite | Al4.33(AlSi3O10)(OH)8 |
| 9.EC.60 | Dozyite | Mg7Al2(Al2Si4O15)(OH)12 |
| 9.EC.60 | Rectorite | (Na,Ca)Al4((Si,Al)8O20)(OH)4 · 2H2O |
| 9.EC.60 | Corrensite | (Mg,Fe)9((Si,Al)8O20)(OH)10 · nH2O |
| 9.EC.60 | Aliettite | Ca0.2Mg6((Si,Al)8O20)(OH)4 · 4H2O |
| 9.EC.60 | Karpinskite | (Ni,Mg)2Si2O5(OH)2 (?) |
| 9.EC.60 | Lunijianlaite | Li0.7Al6.2(AlSi7O20)(OH,O)10 |
| 9.EC.60 | Tosudite | Na0.5(Al,Mg)6((Si,Al)8O18)(OH)12 · 5H2O |
| 9.EC.60 | Hydrobiotite | K(Mg,Fe2+)6((Si,Al)8O20)(OH)4 · nH2O |
| 9.EC.60 | Saliotite | (Li,Na)Al3(AlSi3O10)(OH)5 |
| 9.EC.60 | Kulkeite | Mg8Al(AlSi7O20)(OH)10 |
| 9.EC.60 | Brinrobertsite | Na0.3Al4(Si4O10)2(OH)4 · 3.5 H2O |
| 9.EC.65 | Macaulayite | (Fe,Al)24Si4O43(OH)2 |
| 9.EC.70 | Burckhardtite | Pb2(Fe3+Te6+)[AlSi3O8]O6 |
| 9.EC.75 | Niksergievite | (Ba,Ca)2Al3(AlSi3O10)(CO3)(OH)6 · nH2O |
| 9.EC.75 | Ferrisurite | (Pb,Ca)2.4Fe3+2(Si4O10)(CO3)1.7(OH)3 · nH2O |
| 9.EC.75 | Surite | (Pb,Ca)3(Al,Fe2+,Mg)2((Si,Al)4O10)(CO3)2(OH)2 |
| 9.EC.80 | Kegelite | Pb8Al4(Si8O20)(SO4)2(CO3)4(OH)8 |
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) | 2.3745% | 736 | 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.
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
Internet Links for Montdorite
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References for Montdorite
Localities for Montdorite
Showing 3 localities.
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.
Algeria | |
| Eur. J. Mineral. |
France (TL) | |
| Robert et al. (1979) |
Kenya | |
| Mineralogical Magazine et al. (13) |




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The
Charlannes, La Bourboule, Issoire, Puy-de-Dôme, Auvergne-Rhône-Alpes, France