Hydrobiotite
A valid IMA mineral species
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About Hydrobiotite
Formula:
K(Mg,Fe2+)6((Si,Al)8O20)(OH)4 · nH2O
Colour:
Blackish, brownish; golden yellow, pinkish.
Lustre:
Dull
Hardness:
2½ - 3
Specific Gravity:
2.49 - 2.64
Crystal System:
Monoclinic
Name:
Named for resembling biotite in its chemical composition but containing considerably more water.
A 1:1 regular interstratification of Biotite and Vermiculite layers.
Compare the chemically similar stilpnomelane.
See also hydromuscovite.
Compare the chemically similar stilpnomelane.
See also hydromuscovite.
Unique Identifiers
Mindat ID:
1966
Long-form identifier:
mindat:1:1:1966:4
IMA Classification of Hydrobiotite
Approved
IMA status notes:
Renamed by the IMA
IMA Formula:
K(Mg,Fe2+)6(Si,Al)8O20(OH)4·nH2O
Classification of Hydrobiotite
9.EC.60
9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
9 : SILICATES (Germanates)
E : Phyllosilicates
C : Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
71.2.2d.1
71 : PHYLLOSILICATES Sheets of Six-Membered Rings
2 : Sheets of 6-membered rings with 2:1 layers
71 : PHYLLOSILICATES Sheets of Six-Membered Rings
2 : Sheets of 6-membered rings with 2:1 layers
Mineral Symbols
As of 2021 there are now IMAâCNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
Please only use the official IMAâCNMNC symbol. Older variants are listed for historical use only.
Please only use the official IMAâCNMNC symbol. Older variants are listed for historical use only.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Hbt | IMAâCNMNC | Warr, L.N. (2021). IMAâCNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
| Hbt | Warr (2020) | Warr, L.N. (2020) Recommended abbreviations for the names of clay minerals and associated phases. Clay Minerals, 55, 261â264 doi:10.1180/clm.2020.30 |
Pronunciation of Hydrobiotite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Hydrobiotite
Dull
Transparency:
Translucent
Colour:
Blackish, brownish; golden yellow, pinkish.
Hardness:
2½ - 3 on Mohs scale
Tenacity:
Flexible
Cleavage:
Perfect
{001}
{001}
Density:
2.49 - 2.64 g/cm3 (Measured)
Optical Data of Hydrobiotite
Type:
Biaxial (-)
Dispersion:
weak
Pleochroism:
Weak
Comments:
X = light brown; Y = Z = brown.
Comments:
Absorption: X > Y = Z.
Chemistry of Hydrobiotite
Mindat Formula:
K(Mg,Fe2+)6((Si,Al)8O20)(OH)4 · nH2O
Element Weights:
Common Impurities:
Ti,Cr,Mn,Ca,Sr,Ba,Na,Rb,F,P
Crystallography of Hydrobiotite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
C2/m
Cell Parameters:
c = 25.0(5) Å
Comment:
by analogy to biotite and vermiculite
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 12.23 Ă | (60) |
| 3.493 Ă | (50) |
| 4.909 Ă | (30) |
| 2.725 Ă | (20) |
| 2.041 Ă | (16) |
| 3.071 Ă | (15) |
| 24.3 Ă | (7) |
Comments:
Northeastern Transvaal, South Africa. Data from Brindley et al. (1983). The largest intensity in the data for this sample was 60.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 22 : Hydration and low-? subsurface aqueous alteration (see also #23) | |
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] |
Synonyms of Hydrobiotite
Other Language Names for Hydrobiotite
Common Associates
Associations Based on Photo Data:
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(LiAl1.5â»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+â»)(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+Alâ»)(Si4O10)(OH)2 |
| 9.EC.15 | Nanpingite | CsAl2(AlSi3O10)(OH,F)2 |
| 9.EC.15 | Ferroceladonite | K(Fe2+Fe3+â»)(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(MgAlâ»)(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+â»)(Si4O10)(OH)2 |
| 9.EC.15 | Chromceladonite | K(MgCrâ»)(Si4O10)(OH)2 |
| 9.EC.15 | Montdorite | KFe2+1.5Mn2+0.5Mg0.5Si4O10(F,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,â»)(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 | (LiAl4â»)[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 | (LiAl4â»)[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 | 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
Radioactivity:
| Element | % Content | Activity (Bq/kg) | Radiation Type |
|---|---|---|---|
| Uranium (U) | 0.0000% | 0 | α, ÎČ, Îł |
| Thorium (Th) | 0.0000% | 0 | α, ÎČ, Îł |
| Potassium (K) | 4.7935% | 1,486 | ÎČ, Îł |
For comparison:
- Banana: ~15 Bq per fruit
- Granite: 1,000â3,000 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 ”Sv/year. Note that natural background radiation averages around 2400 ”Sv/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: â
| Distance | Dose rate | Risk |
|---|---|---|
| 1âŻcm | ||
| 10âŻcm | ||
| 1âŻm |
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 Hydrobiotite
mindat.org URL:
https://www.mindat.org/min-1966.html
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References for Hydrobiotite
Reference List:
COLEMAN, N. T., LEROUX, F. H., CADY, JOHN G. (1963) Biotite - Hydrobiotite - Vermiculite in Soils. Nature, 198 (4878). 409-410 doi:10.1038/198409c0
Boettcher, A. L. (1966) Vermiculite, hydrobiotite, and biotite in the Rainy Creek igneous complex near Libby, Montana. Clay Minerals, 6 (4) 283-296 doi:10.1180/claymin.1966.006.4.03
Localities for Hydrobiotite
Showing 66 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
â - 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.
Australia | |
| Crohn et al. (1984) |
| Simpson (1948) |
Austria | |
| Götzinger (1987) |
| Database âMinerale NĂâ (A. Thinschmidt and co-workers) |
| Götzinger (1987) |
| Postl et al. (2026) |
| R. Dallinger & J. Gufler (2006) |
Brazil | |
| de Lima et al. (2023) |
Canada | |
| Peatfield (n.d.) |
| Ray et al. (2002) |
| reprinted in: Rocks & Minerals (4) +1 other reference |
Chile | |
| Lohmeier et al. (2025) |
China | |
| Mao Xingli and Yan Yipeng (1987) |
| Gansu Province Metallurgical and Geological Exploration Team No. 4 (1978) |
| Ottens (2011) |
| Cui et al. (2023) |
| Zongyao et al. (2005) |
| Kuanglin Yan (1978) |
| Ran Hongyan et al. (1999) |
| Xue et al. (2022) |
| Ding et al. (2025) |
Egypt | |
| Harraz +1 other reference |
France | |
| Forestier (1964) |
| Forestier (1964) +1 other reference |
| Leblanc et al. (1987) |
| |
| Forestier (1964) |
| Forestier (1964) |
| Forestier (1964) | |
Georgia | |
| Gugushvili et al. (2002) |
Hungary | |
| Koch (1985) |
India | |
| S. G. Tenainkai et al. (1991) |
Italy | |
| M.E. Ciriotti (2006) |
Japan | |
| Sadanaga et al. (1974) |
| Cureton Minerals Co |
| Sadanaga et al. (1974) |
Mexico | |
| Panczner (1987) |
Pacific Ocean | |
| Fengyou Chu et al. (2006) |
| Astakhova et al. (2014) |
Poland | |
| HaraĆczyk C. (1970) |
Russia | |
| Igor Pekov and Anatoly Kasatkin analytical data (2011) |
| webmineral.ru (2016) | |
| Kasatkin et al. (2014) |
Slovakia | |
| OzdĂn et al. (2017) |
South Africa | |
| FĂ€rber (n.d.) +1 other reference |
Spain | |
| Pascual +1 other reference |
USA | |
| Anthony et al. (1995) |
| Anthony et al. (1995) |
| Schwartz (1947) +3 other references |
| . +4 other references | |
| Eckel et al. (1997) |
| Wayne C. Shanks et al. (2012) | |
| Meeker et al. (2003) |
| Tucker (n.d.) +2 other references |
| Castor et al. (2004) |
| Castor et al. (2004) |
| Dana et al. (1892) | |
| Genth (1891) |
| Eckert | |
| |
| ... |
| Dietrich (1990) |
| Dietrich (1990) |
| Dietrich (1990) |
Zimbabwe | |
| Tyndale-Biscoe (1951) |
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Montenero Quarry, Onano, Viterbo Province, Lazio, Italy