Bentorite
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About Bentorite
Formula:
Ca6Cr2(SO4)3(OH)12 · 26H2O
Cr(III) may be partly replaced by Al.
Colour:
Violet to rose-purple
Lustre:
Resinous, Waxy, Earthy
Hardness:
2
Specific Gravity:
2.025
Crystal System:
Trigonal
Member of:
Name:
Named in 1977 by Shulamit Gross in honor of Professor Yaakov K. Ben-Tor [February 13, 1910 Königsberg, East Prussia, Germany - October 29, 2002 La Jolla, California, USA], petrologist and geologist, Scripps Institute of Oceanography, University of California, San Diego, California, USA and Department head of Geology, Hebrew University, Jerusalem, Israel from 1954-1966, for his contributions to the geology and mineralogy of Israel and the Middle East.
Type Locality:
Classification of Bentorite
Approved
Approval year:
1979
6/D.13-20
7.DG.15
7.DG.15
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
G : With large and medium-sized cations; with NO3, CO3, B(OH)4, SiO4 or IO3
7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H2O
G : With large and medium-sized cations; with NO3, CO3, B(OH)4, SiO4 or IO3
31.10.2.2
31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
10 : Miscellaneous
31 : HYDRATED SULFATES CONTAINING HYDROXYL OR HALOGEN
10 : Miscellaneous
25.4.14
25 : Sulphates
4 : Sulphates of Ca, Sr and Ba
25 : Sulphates
4 : Sulphates of Ca, Sr and Ba
Physical Properties of Bentorite
Resinous, Waxy, Earthy
Transparency:
Transparent
Comment:
Originally said to be vitreous
Colour:
Violet to rose-purple
Streak:
Very pale purple
Hardness:
2 on Mohs scale
Cleavage:
Perfect
{1010} perfect; {0001} good
{1010} perfect; {0001} good
Fracture:
Sub-Conchoidal
Density:
2.025 g/cm3 (Measured) 2.021 g/cm3 (Calculated)
Optical Data of Bentorite
Type:
Uniaxial (+)
RI values:
nω = 1.478 nε = 1.484
Birefringence:
0.006
Max Birefringence:
δ = 0.006
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
and does not take into account mineral colouration.
Surface Relief:
Moderate
Optical Extinction:
Parallel
Pleochroism:
Visible
Comments:
O = colorless; E = pale violet purple
Comments:
Absorption E > O
Chemical Properties of Bentorite
Formula:
Ca6Cr2(SO4)3(OH)12 · 26H2O
Cr(III) may be partly replaced by Al.
Cr(III) may be partly replaced by Al.
Crystallography of Bentorite
Crystal System:
Trigonal
Class (H-M):
3m - Ditrigonal Pyramidal
Space Group:
P3 1c
Cell Parameters:
a = 11.1927 (5) Å, c = 21.7121(5) Å
Ratio:
a:c = 1 : 1.94
Unit Cell V:
2,355.60 ų (Calculated from Unit Cell)
Z:
2
Morphology:
Euhedral crystals very rare. Minute crystals (<< 1 mm) show first- and second-order prisms.
Twinning:
{1010}
X-Ray Powder Diffraction
Image Loading
Radiation - Copper Kα
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 9.66 Å | (100) |
| 5.59 Å | (40) |
| 3.89 Å | (10) |
| 3.60 Å | (10) |
| 3.23 Å | (10) |
| 2.77 Å | (10) |
| 2.21 Å | (10) |
| 1.94 Å | (20) |
Comments:
ICDD 33-248
Type Occurrence of Bentorite
General Appearance of Type Material:
Fine-grained deep purple to light rosey purple masses and veinlet filling.
Geological Setting of Type Material:
Auto-metamorphosed marble: Hatrurim Formation
Associated Minerals at Type Locality:
Synonyms of Bentorite
Other Language Names for Bentorite
Relationship of Bentorite to other Species
Member of:
Other Members of this group:
| Buryatite | Ca3(Si,Fe3+,Al)(SO4)B(OH)4(OH,O)6 · 12H2O | Trig. 3m : P3 1c |
| Carraraite | Ca3(SO4)[Ge(OH)6](CO3) · 12H2O | Hex. |
| Charlesite | Ca6(Al,Si)2(SO4)2[B(OH)4](OH,O)12 · 26H2O | Trig. 3m : P3 1c |
| Chiyokoite | Ca3Si(CO3)[B(OH)4]O (OH)5 · 12H2O | Hex. 6 : P63 |
| Ettringite | Ca6Al2(SO4)3(OH)12 · 26H2O | Trig. 3m : P3 1c |
| Hielscherite | Ca3Si(SO4)(SO3)(OH)6 · 11H2O | Hex. 6 : P63 |
| Imayoshiite | Ca3Al(CO3)[B(OH)4](OH)6 · 12H2O | Hex. 6 : P63 |
| Jouravskite | Ca3Mn4+(SO4)(CO3)(OH)6 · 12H2O | Hex. 6 : P63 |
| Kottenheimite | Ca 3Si(SO4)2(OH)6 · 12H2O | Hex. 6/m : P63/m |
| Micheelsenite | (Ca2Y)Al(PO3OH)(CO3)(OH)6 · 12H2O | Hex. 6 : P63 |
| Siwaqaite | Ca6Al2(CrO4)3(OH)12 · 26H2O | Trig. 3m : P3 1c |
| Sturmanite | Ca6Fe3+2(SO4)2.5[B(OH)4](OH)12 · 25H2O | Trig. 3m : P3 1c |
| Tatarinovite | Ca3Al(SO4)[B(OH)4](OH)6 · 12H2O | Hex. 6 : P63 |
| Thaumasite | Ca3(SO4)[Si(OH)6](CO3) · 12H2O | Hex. 6 : P63 |
| UM2008-07-CO:AlBCaHSSi | Ca6(Al,Si)2(CO3,SO4)2[B(OH)4](OH,O)12 · 26H2O | |
| Unnamed (possible Mn(IV) analogue of Sturmanite) | Ca6Mn4+2(SO4)2[B(OH)4](OH)10O2 · nH2O |
Related Minerals - Nickel-Strunz Grouping
| 7.DG. | Mathesiusite | K5(UO2)4(SO4)4(VO5) · 4H2O | Tet. 4/m : P4/n |
| 7.DG.05 | Darapskite | Na3(SO4)(NO3) · H2O | Mon. 2/m |
| 7.DG.10 | Clinoungemachite | (Na, K, Fe, SO4) | Mon. 2/m |
| 7.DG.10 | Humberstonite | Na7K3Mg2(SO4)6(NO3)2 · 6H2O | Trig. 3 : R3 |
| 7.DG.10 | Ungemachite | K3Na8Fe(SO4)6(NO3)2 · 6H2O | Trig. 3 : R3 |
| 7.DG.15 | Charlesite | Ca6(Al,Si)2(SO4)2[B(OH)4](OH,O)12 · 26H2O | Trig. 3m : P3 1c |
| 7.DG.15 | Ettringite | Ca6Al2(SO4)3(OH)12 · 26H2O | Trig. 3m : P3 1c |
| 7.DG.15 | Jouravskite | Ca3Mn4+(SO4)(CO3)(OH)6 · 12H2O | Hex. 6 : P63 |
| 7.DG.15 | Sturmanite | Ca6Fe3+2(SO4)2.5[B(OH)4](OH)12 · 25H2O | Trig. 3m : P3 1c |
| 7.DG.15 | Thaumasite | Ca3(SO4)[Si(OH)6](CO3) · 12H2O | Hex. 6 : P63 |
| 7.DG.15 | Carraraite | Ca3(SO4)[Ge(OH)6](CO3) · 12H2O | Hex. |
| 7.DG.15 | Buryatite | Ca3(Si,Fe3+,Al)(SO4)B(OH)4(OH,O)6 · 12H2O | Trig. 3m : P3 1c |
| 7.DG.20 | Rapidcreekite | Ca2(SO4)(CO3) · 4H2O | Orth. |
| 7.DG.20 | Korkinoite | Ca4(SO4)2(CO3)2 · 9(H2O) | Orth. mmm (2/m 2/m 2/m) : Pmmm |
| 7.DG.25 | Tatarskite | Ca6Mg2(SO4)2(CO3)2(OH)4Cl4 · 7H2O | Orth. |
| 7.DG.30 | Nakauriite | Cu8(SO4)4(CO3)(OH)6 · 48H2O | Orth. |
| 7.DG.35 | Chessexite | (Na,K)4Ca2(Mg,Zn)3Al8(SO4)10(SiO4)2 · 40H2O | Orth. |
| 7.DG.40 | Carlosruizite | K6(Na,K)4Na6Mg10(SeO4)12(IO3)12 · 12H2O | Trig. 3m (3 2/m) : P3c1 |
| 7.DG.40 | Fuenzalidaite | K6(Na,K)4Na6Mg10(SO4)12(IO3)12 · 12H2O | Trig. 3m (3 2/m) : P3c1 |
| 7.DG.45 | Chelyabinskite | (Ca,Mg)3(SO4,CO3)2[Si(OH)6] · 9H2O (?) | Orth. |
Related Minerals - Dana Grouping (8th Ed.)
| 31.10.2.1 | Ettringite | Ca6Al2(SO4)3(OH)12 · 26H2O | Trig. 3m : P3 1c |
Related Minerals - Hey's Chemical Index of Minerals Grouping
| 25.4.1 | Anhydrite | CaSO4 | Orth. mmm (2/m 2/m 2/m) |
| 25.4.2 | Bassanite | Ca(SO4) · 0.5H2O | Mon. 2 : B2 |
| 25.4.3 | Gypsum | CaSO4 · 2H2O | Mon. 2/m |
| 25.4.4 | Glauberite | Na2Ca(SO4)2 | Mon. 2/m : B2/b |
| 25.4.5 | Cesanite | Na3Ca2(SO4)3(OH) | Hex. 6 : P6 |
| 25.4.6 | Eugsterite | Na4Ca(SO4)3 · 2H2O | Mon. |
| 25.4.7 | Hydroglauberite | Na10Ca3(SO4)8 · 6H2O | Mon. |
| 25.4.8 | Syngenite | K2Ca(SO4)2 · H2O | Mon. 2/m : P21/m |
| 25.4.9 | Görgeyite | K2Ca5(SO4)6 · H2O | Mon. |
| 25.4.10 | Polyhalite | K2Ca2Mg(SO4)4 · 2H2O | Tric. 1 |
| 25.4.11 | Koktaite | (NH4)2Ca(SO4)2 · H2O | Mon. |
| 25.4.12 | Ye'elimite | Ca4Al6(SO4)O12 | Iso. |
| 25.4.13 | Ettringite | Ca6Al2(SO4)3(OH)12 · 26H2O | Trig. 3m : P3 1c |
| 25.4.15 | Celestine | SrSO4 | Orth. mmm (2/m 2/m 2/m) : Pnma |
| 25.4.16 | Kalistrontite | K2Sr(SO4)2 | Trig. |
| 25.4.17 | Baryte | BaSO4 | Orth. mmm (2/m 2/m 2/m) : Pnma |
Fluorescence of Bentorite
Not fluorescent
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.
References for Bentorite
Reference List:
Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Gross, S. (1980) Bentorite. A new mineral from the Hatrurim Area, west of the Dead Sea, Israel. Israel J. of Earth Sci., 29, 81–84. [abstract in Amer. Mineral., 66 (1981), 639]
Yurii V. Seryotkin, Ella V. Sokol, Svetlana N. Kokh, Mikhail N. Murashko (2018): Natural Cr3+-rich ettringite: occurrence, properties, and crystal structure. Phys. Chem. Minerals 45, 279-292. [Cr/(Cr + Al) ratios up to 0.40–0.50]
Juroszek, R.; Krüger, B.; Galuskina, I.; Krüger, H.; Tribus, M.; Kürsten, C. (2020) Raman Spectroscopy and Single-Crystal High-Temperature Investigations of Bentorite, Ca6Cr2(SO4)3(OH)12·26H2O. Minerals 10, 38.
Internet Links for Bentorite
mindat.org URL:
https://www.mindat.org/min-627.html
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Localities for Bentorite
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for 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.
Israel | |
| Juroszek, R.; Krüger, B.; Galuskina, I.; Krüger, H.; Tribus, M.; Kürsten, C. (2020) Raman Spectroscopy and Single-Crystal High-Temperature Investigations of Bentorite, Ca6Cr2(SO4)3(OH)12·26H2O. Minerals 10, 38. |
Middle East (TL) | |
| Gross, S. (1977): The Mineralogy of the Hatrurim Formation, Israel. Geological Survey of Israel, Bulletin no. 70, 80 pp. |
Palestine | |
| Ella V. Sokol, Olga L. Gaskova, Svetlana N. Kokh, Olga A. Kozmenko, Yuri V. Seryotkin, Yevgeny Vapnik, and Michail N. Murashko (2011): Chromatite and its Cr3+- and Cr6+-bearing precursor minerals from the Nabi Musa Mottled Zone complex, Judean Desert. American Mineralogist, 96, 659-674. |
| Sokol, E.V., Gaskova, O.L., Kokh, S.N., Kozmenko, O.A., Seryotkin, Y.V., Vapnik, Y., Murashko, M.N. (2011): Chromatite and its Cr3+- and Cr6+-bearing precursor minerals from the Nabi Musa Mottled Zone complex, Judean Desert. American Mineralogist 96, 659-674.; Natural History Museum Vienna collection; http://nnhc.huji.ac.il/mineralogy-petrology/?page_id=70&lang=en; Juroszek, R.; Krüger, B.; Galuskina, I.; Krüger, H.; Tribus, M.; Kürsten, C. (2020) Raman Spectroscopy and Single-Crystal High-Temperature Investigations of Bentorite, Ca6Cr2(SO4)3(OH)12·26H2O. Minerals 10, 38. |
Hatrurim Formation, Middle East