Brammallite Mineral Data

General Brammallite Information

Chemical Formula:

(Na,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]

Composition:

Molecular Weight = 391.86 gm

Sodium 3.87 % Na 5.22 % Na₂O

Magnesium 3.72 % Mg 6.17 % MgO

Aluminum 13.77 % Al 26.02 % Al₂O₃

Iron 1.43 % Fe 1.83 % FeO

Silicon 21.50 % Si 46.00 % SiO₂

Hydrogen 1.28 % H 11.47 % H₂O

Oxygen 54.43 % O

______ ______

100.00 % 96.71 % = TOTAL OXIDE

Empirical Formula:

Na_0.66(H₃O)_0.33AlMg_0.6Fe²⁺_0.1Si₃AlO₁₀(OH)₂ï¿½(H₂O)

Environment:

Believed to be a degradation product of paragonite. Group name for Interlayer-deficient clays.

IMA Status:

Not Approved IMA 1998

Locality:

Landebie, Dyfed, Wales. Link to MinDat.org Location Data.

Name Origin:

Named in 1943 for Alfred Brammall (1879-?), British gologist and mineralogist.

Name Pronunciation:

Brammallite + Pronunciation

Synonym:

Hydroparagonite

Sodium hydromica

Sodium illite

Brammallite Image

Images:

Brammallite

Comments: Dark gray-brown fine grained massive brammallite.
Location: Near Ione, Amador County, California, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Brammallite Crystallography

Axial Ratios:

a:b:c =0.5746:1:2.1616

Cell Dimensions:

a = 5.12, b = 8.91, c = 19.26, Z = 4; beta = 95.83° V = 874.08 Den(Calc)= 2.98

Crystal System:

Monoclinic - Prismatic H-M Symbol (2/m) Space Group: C 2/c

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

By Intensity(I/I_o): 1.485(1), 9.77(1), 3.17(1),4.41(0.9), 2.54(0.9), 4.78(0.8), 2.11(0.6), 2.41(0.6),

Physical Properties of Brammallite

Cleavage:

{001} Perfect

Color:

White.

Density:

2.83 - 2.88, Average = 2.85

Diaphaneity:

Translucent

Fracture:

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

Habit:

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

Hardness:

2.5-3 - Finger Nail-Calcite

Luster:

Earthy (Dull)

Streak:

white

Optical Properties of Brammallite

Gladstone-Dale:

CI meas= 0.065 (Fair) - where the CI = (1-KPDmeas/KC)
CI calc= 0.105 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1918,KPDmeas= 0.2002,KC= 0.2142
Ncalc = 1.61 - 1.64

Optical Data:

Biaxial (-), a=1.535-1.57, b=1.555-1.6, g=1.565-1.605, bire=0.0300-0.0350, 2V(Calc)=42-68, 2V(Meas)=5-25. Dispersion none.

Pleochroism (x):

colorless.

Pleochroism (y):

colorless.

Pleochroism (z):

colorless.

Calculated Properties of Brammallite

Electron Density:

Bulk Density (Electron Density)=2.87 gm/cc
note: Specific Gravity of Brammallite =2.86 gm/cc.

Fermion Index:

Fermion Index = 0.01
Boson Index = 0.99

Photoelectric:

PE_Brammallite= 1.83 barns/electron
U=PE_Brammallite x rElectron Density= 5.23 barns/cc.

Radioactivity:

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

Brammallite Classification

Dana Class:

71.02.02d.04 (71)Phyllosilicate Sheets of Six-Membered Rings

(71.02)with 2:1 Layers

(71.02.02d)Mica Group (Hydromica subgroup)

71.02.02d.01 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

71.02.02d.02 Illite* (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/m 2/m

71.02.02d.03 Vermiculite (Mg,Fe,Al)3(Al,Si)4O10(OH)2•4(H2O) C 2/m 2/m

71.02.02d.04 Brammallite* (Na,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/c 2/m

Strunz Class:

09.EC.25 09 - SILICATES (Germanates)

09.E - Phyllosilicates

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

09.EC.25 Brammallite* (Na,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)] C 2/c 2/m

Other Brammallite Information

References:

NAME( Dana8) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)

See Also:

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

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Print or Cut-and-Paste your Brammallite Specimen Label here :

Brammallite

(Na,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]
Dana No: 71.02.02d.04 Strunz No: 09.EC.25
Locality:

Notes:

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