Brinrobertsite Mineral Data

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General Brinrobertsite Information

Chemical Formula:

(Na,K,Ca)x(Al,Fe,Mg)4(Si,Al)8O20(OH)4•3.54(H2O) [x = 0.35, n = 3.54]

Composition:

Molecular Weight = 957.70 gm

Potassium 0.29 % K 0.34 % K₂O

Sodium 0.53 % Na 0.71 % Na₂O

Calcium 0.25 % Ca 0.35 % CaO

Magnesium 0.20 % Mg 0.34 % MgO

Aluminum 11.18 % Al 21.13 % Al₂O₃

Iron 0.47 % Fe 0.60 % FeO

Silicon 22.99 % Si 49.19 % SiO₂

Hydrogen 3.06 % H 27.34 % H₂O

Oxygen 61.03 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

Na_0.22K_0.07Ca_0.06Al_3.81Mg_0.08Fe²⁺_0.08Si_7.84Al_0.16O₂₀(OH)₄3.54(H₂O)_3.54

Environment:

Found in an Ordovician soapy mudtone (metabentonite). Altered from ash (glass) with pyrophyllite as the precursor mineral.

IMA Status:

Approved IMA 2002 (Dana # Added)

Locality:

Bangor, North Wales, England, Great Britain Link to MinDat.org Location Data.

Name Origin:

Named for Brin Roberts, specialist for British clay minerals in the University of London.

Synonym:

IMA1997-040

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Brinrobertsite Crystallography

Axial Ratios:

a:b:c =0.5714:1:2.6813

Cell Dimensions:

a = 5.2, b = 9.1, c = 24.4, Z = 2; beta = 90° V = 1,154.61 Den(Calc)= 2.75

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: pseudo 2/m

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

By Intensity(I/I_o): 10.99(1)(002), 22.29(0.48)(001), 3.17(0.33)(007),5.48(0.07)(004), 2.01(0.04)(0.0.11),

Physical Properties of Brinrobertsite

Cleavage:

{001} Perfect

Color:

Gray, Yellowish gray.

Diaphaneity:

Transparent

Habit:

Anhedral Grains - Granular minerals without the expression of crystal shapes

Habit:

Earthy - Dull, clay-like texture with no visible crystalline affinities, (e.g. howlite).

Habit:

Microscopic Crystals - Crystals visible only with microscopes.

Luster:

Earthy (Dull)

Streak:

white

Optical Properties of Brinrobertsite

Optical Data:

Biaxial (?)

NCalc= 1.67 - from Gladstone-Dale relationship (KC = 0.2436) where Ncalc=Dcalc*KC+1

Calculated Properties of Brinrobertsite

Electron Density:

Bulk Density (Electron Density)=2.82 gm/cc
note: Specific Gravity of Brinrobertsite =2.75 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_{Brinrobertsite}= 1.48 barns/electron
U=PE_{Brinrobertsite} x r_electron= 4.17 barns/cc.

Radioactivity:

GRapi = 4.25 (Gamma Ray American Petroleum Institute Units)
Concentration of Brinrobertsite per GRapi unit = 23.56 (%)

Estimated Radioactivity from Brinrobertsite - barely detectable

Brinrobertsite Classification

Dana Class:

71.02.01.06 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.02)with 2:1 Layers

(71.02.01)Pyrophyllite-talc group

71.02.01.01 Pyrophyllite Al2Si4O10(OH)2 P1 1

71.02.01.02 Ferripyrophyllite Fe2Si4O10(OH)2 C 2/m 2/m

71.02.01.03 Talc Mg3Si4O10(OH)2 C 2/c 2/m

71.02.01.04 Willemseite (Ni,Mg)3Si4O10(OH)2 C 2/c 2/m

71.02.01.05 Minnesotaite (Fe,Mg)3Si4O10(OH)2 C1 1

71.02.01.06 Brinrobertsite! (Na,K,Ca)x(Al,Fe,Mg)4(Si,Al)8O20(OH)4•3.54(H2O)[x=0.35,n=3.54] pseudo 2/m 2/m

Strunz Class:

09.EC.60 09 - SILICATES (Germanates)

09.E - Phyllosilicates

09.EC -Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets

09.EC.60 Aliettite [Mg3Si4O10(OH)2](Ca0.5,Na)0.33(Al,Mg,Fe)2-3(Si,Al)4O10(OH)2•n(H2O) Unk Mono

09.EC.60 Dozyite (Mg7Al2)(Si4Al2)O15(OH)12 Cm m

09.EC.60 Corrensite (Ca,Na,K)(Mg,Fe,Al)9(Si,Al)8O20(OH)10•n(H2O) Unk Ortho

09.EC.60 Kulkeite Na0.35Mg8AlSi7O20(OH)10 Unk Mono

09.EC.60 Karpinskite (Mg,Ni)2Si2O5(OH)2(?) Unk Mono

09.EC.60 Illite* (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/m 2/m

09.EC.60 Hydrobiotite [K(Mg,Fe)3(Al,Fe)Si3O10(OH,F)2]•[(Mg,Fe,Al)3(Si,Al)4O10(OH)2•4(H2O)] C 2/m 2/m

09.EC.60 Lunijianlaite LiAl6(Si7Al)O20(OH)10 Unk Mono

09.EC.60 Rectorite (Na,Ca)Al4(Si,Al)8O20(OH)4•2(H2O) Unk Mono

09.EC.60 Saliotite Na0.5Li0.5Al3AlSi3O10(OH)5 C 2/m 2/m

09.EC.60 Tosudite Na0,5(Al,Mg)6(Si,Al)8O18(OH)12•5(H2O) Unk Ortho

09.EC.60 Brinrobertsite! (Na,K,Ca)x(Al,Fe,Mg)4(Si,Al)8O20(OH)4•3.54(H2O)[x=0.35,n=3.54] pseudo 2/m 2/m

Other Brinrobertsite Information

References:

NAME( AmMin, v 88, p 931) PHYS. PROP.(AmMin, v 88, p 931)

See Also:

Links to other databases for Brinrobertsite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - GeoScienceWorld
4 - Google Images
5 - Google Scholar
6 - MinDAT
7 - Mineralienatlas (Deutsch)
8 - Online Mineral Museum
9 - QUT Mineral Atlas
10 - Ruff.Info

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Brinrobertsite

(Na,K,Ca)x(Al,Fe,Mg)4(Si,Al)8O20(OH)4•3.54(H2O) [x = 0.35, n = 3.54]
Dana No: 71.02.01.06 Strunz No: 09.EC.60
Locality:

Notes: