Brinrobertsite Mineral Data

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 = 762.30 gm

Potassium 0.51 % K 0.62 % K₂O

Sodium 0.60 % Na 0.81 % Na₂O

Calcium 0.32 % Ca 0.44 % CaO

Magnesium 0.32 % Mg 0.53 % MgO

Aluminum 10.62 % Al 20.06 % Al₂O₃

Iron 0.73 % Fe 0.94 % FeO

Silicon 27.63 % Si 59.11 % SiO₂

Hydrogen 1.47 % H 13.09 % H₂O

Oxygen 57.80 % O

______ ______

100.00 % 95.61 % = TOTAL OXIDE

Empirical Formula:

Na_0.2K_0.1Ca_0.06Al_2.8Fe²⁺_0.1Mg_0.1Si_7.5Al_0.2O₂₀(OH)₄·3.54(H₂O)

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)= 2.19

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.

Diaphaniety:

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= 1.47 - from Gladstone-Dale relationship (KC = 0.2155) where Ncalc=Dcalc*KC+1

Calculated Properties of Brinrobertsite

Electron Density:

r_electron=2.21 gm/cc
note: r_{Brinrobertsite}=2.19 gm/cc.

Fermion Index

Fermion Index = 0.01366
Boson Index = 0.98634

Photoelectric:

PE_{Brinrobertsite}= 1.74 barns/electron
U=PE_{Brinrobertsite} x r_electron= 3.84 barns/cc.

Radioactivity:

GRapi = 7.45 (Gamma Ray American Petroleum Institute Units)

Estimated Radioactivity from Brinrobertsite - barely detectable

Brinrobertsite Classification

Dana Class:

71.2.1.6 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.2)with 2:1 Layers

(71.2.1)Pyrophyllite-talc group

71.2.1.1 Pyrophyllite Al2Si4O10(OH)2 P1 1

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

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

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

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

71.2.1.6 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:

VIII/H.19-10a VIII - Silicates

VIII/H - Phyllosilicates (layered) Mica like with [Si4O10]4- and related groups

VIII/H.19 - Brammallite ? - Yakhontovite series

VIII/H.19-10 Brammallite* (Na,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/c 2/m

VIII/H.19-10a 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

VIII/H.19-15 Illite* (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/m 2/m

VIII/H.19-20 Montmorillonite (Na,Ca)0,3(Al,Mg)2Si4O10(OH)2·n(H2O) C 2/m 2/m

VIII/H.19-30 Beidellite Na0.5Al2(Si3.5Al0.5)O10(OH)2·n(H2O) C 2/m or ORTH 2/m

VIII/H.19-40 Nontronite Na0.3Fe2(Si,Al)4O10(OH)2·n(H2O) C 2/m 2/m

VIII/H.19-50 Volkonskoite Ca0.3(Cr,Mg,Fe)2(Si,Al)4O10(OH)2·4(H2O) C 2/m 2/m

VIII/H.19-60 Swinefordite (Li,Ca0.5,Na)0.72(Li,Al,Mg)2.66(Si,Al)4O10(OH,F)2·2(H2O) C 2/m (MON or ORTH) 2/m

VIII/H.19-70 Yakhontovite (Ca,K)0.5(Cu,Fe,Mg)2Si4O10(OH)2·3(H2O) C 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 -Google Images 4 -Google Scholar 5 -MinDAT 6 -MinMax(Deutsch) 7 -MinMax(English) 8 -Mineralienatlas (Deutsch) 9 -QUT Mineral Atlas

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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: 71.2.1.6 Strunz No: VIII/H.19-10a
Locality:

Notes: