Bentorite Mineral Data

General Bentorite Information

Chemical Formula:

Ca6(Cr,Al)2(SO4)3(OH)12•26(H2O)

Composition:

Molecular Weight = 1,292.63 gm

Calcium 18.60 % Ca 26.03 % CaO

Aluminum 1.04 % Al 1.97 % Al₂O₃

Chromium 6.03 % Cr 8.82 % Cr₂O₃

Hydrogen 4.99 % H 44.60 % H₂O

Sulfur 7.44 % S 18.58 % SO₃

Oxygen 61.89 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Ca₆Cr_1.5Al_0.5(SO₄)₃(OH)₁₂•26(H₂O)

Environment:

Low-temperature hydrothermal veins in black calciteï¿½spurrite marble.

IMA Status:

Approved IMA 1980

Locality:

Marble quarry in the Hatrurim Formation, near the Arad-Sodom road, Negev Desert, Israel. Link to MinDat.org Location Data.

Name Origin:

Named for Y.K. Bentor, Professor at the University of California, San Diego, California, USA, for his contributions to geology and mineralogy in Israel.

Name Pronunciation:

Bentorite + Pronunciation

Bentorite Image

Images:

Bentorite

Comments: Violet crystalline bentorite.
Location: Hatrurim Area, West of Dead Sea, Israel. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Bentorite Crystallography

Axial Ratios:

a:c = 1:0.95794

Cell Dimensions:

a = 22.35, c = 21.41, Z = 8; V = 9,261.95 Den(Calc)= 1.85

Crystal System:

Hexagonal - Dihexagonal Dipyramidal H-M Symbol (6/m 2/m 2/m) Space Group: P 6₃/mmc

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 9.656(1), 5.592(0.4), 1.942(0.2),

Physical Properties of Bentorite

Cleavage:

{1010} Perfect

Color:

Violet, Light violet.

Density:

2.025

Diaphaneity:

Transparent

Hardness:

2 - Gypsum

Luster:

Vitreous (Glassy)

Streak:

violet

Optical Properties of Bentorite

Gladstone-Dale:

CI meas= 0.116 (Poor) - where the CI = (1-KPDmeas/KC)
CI calc= 0.033 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.26,KPDmeas= 0.2375,KC= 0.2688
Ncalc = 1.5 - 1.54

Optical Data:

Uniaxial (+), w=1.478, e=1.484, bire=0.0060.

Calculated Properties of Bentorite

Electron Density:

Bulk Density (Electron Density)=1.93 gm/cc
note: Specific Gravity of Bentorite =1.85 gm/cc.

Fermion Index:

Fermion Index = 0.0068459104
Boson Index = 0.9931540896

Photoelectric:

PE_Bentorite= 4.06 barns/electron
U=PE_Bentorite x rElectron Density= 7.84 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Bentorite is Not Radioactive

Bentorite Classification

Dana Class:

31.10.02.02 (31)Hydrated Sulfates Containing Hydroxyl or Halogen

(31.10)miscellaneous

(31.10.02)Dana Group

31.10.02.01 Ettringite Ca6Al2(SO4)3(OH)12•26(H2O) P 6₃/mmc 6/m 2/m 2/m

31.10.02.02 Bentorite Ca6(Cr,Al)2(SO4)3(OH)12•26(H2O) P 6₃/mmc 6/m 2/m 2/m

31.10.02.03 Buryatite! Ca3(Si,Fe,Al)[SO4][B(OH)4](OH,O)6•12(H2O) P 3₁c 3m

Strunz Class:

07.DG.15 07 - SULFATES (SELENATES, TELLURATES)

07.D - Sulfates (selenates, etc.) with additional anions, with H2O

07.DG -With large and medium sized cations; with NO3, CO3, B(OH)4, SiO4 or IO3

07.DG.15 Bentorite Ca6(Cr,Al)2(SO4)3(OH)12•26(H2O) P 6₃/mmc 6/m 2/m 2/m

07.DG.15 Charlesite Ca6(Al,Si)2(SO4)2B(OH)4(OH,O)12•26(H2O) P 3₁c 3m

07.DG.15 Ettringite Ca6Al2(SO4)3(OH)12•26(H2O) P 6₃/mmc 6/m 2/m 2/m

07.DG.15 Jouravskite Ca3Mn(SO4,CO3)2(OH)6•12(H2O) P 6₃/m 6/m

07.DG.15 Sturmanite Ca6(Fe,Al,Mn)2(SO4)2[B(OH)4](OH)12•25(H2O) P 3₁c 3m

07.DG.15 Thaumasite Ca3Si(CO3)(SO4)(OH)6•12(H2O) P 6₃/m 6/m

07.DG.15 Buryatite! Ca3(Si,Fe,Al)[SO4][B(OH)4](OH,O)6•12(H2O) P 3₁c 3m

07.DG.15 Carraraite! Ca3Ge(OH)6(SO4)(CO3)•12H2O P 6₃/m, or P 6₃ Hex

Other Bentorite Information

References:

NAME( AntBidBlaNic5) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

Links to other databases for Bentorite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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Bentorite

Ca6(Cr,Al)2(SO4)3(OH)12•26(H2O)
Dana No: 31.10.02.02 Strunz No: 07.DG.15
Locality:

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