Bracewellite Mineral Data

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General Bracewellite Information

Chemical Formula:

Cr+++O(OH)

Composition:

Molecular Weight = 85.00 gm

Chromium 61.17 % Cr 89.40 % Cr₂O₃

Hydrogen 1.19 % H 10.60 % H₂O

Oxygen 37.64 % O

______ ______

100.00 % 100.00 % = TOTAL OXIDE

Empirical Formula:

CrO(OH)

Environment:

Adjacent to an incrusting ullmannite in oxidized hydrothermal base-metal deposits.

IMA Status:

Approved IMA 1967

Locality:

Merume River Basin, Mazaruni, Guyana Link to MinDat.org Location Data.

Name Origin:

Named after Smith Bracewell, Director of the British Guiana (now Guyana) Geological Survey.

Name Pronunciation:

Bracewellite + Pronunciation

Synonym:

ICSD 27517

PDF 25-1497

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Bracewellite Crystallography

Axial Ratios:

a:b:c =0.4555:1:0.3016

Cell Dimensions:

a = 4.492, b = 9.86, c = 2.974, Z = 4; V = 131.72 Den(Calc)= 4.29

Crystal System:

Orthorhombic - DipyramidalH-M Symbol (2/m 2/m 2/m) Space Group: Pbnm

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

By Intensity(I/I_o): 4.09(1), 2.65(0.8), 2.546(0.7),

Crystal Structure:

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Milton C , Appleman D E , Appleman M H , Chao E C T , Cuttita F , Dinnin J I , Dwornik E J , Ingram B L , Rose H J , U.S. Geological Survey Professional Paper , 887 (1976) p.1-29, Merumite, a complex assemblage of chromium minerals from Guyana, Locality: Guyana

Physical Properties of Bracewellite

Color:

Dark reddish brown, Reddish brown, Black.

Density:

4.45 - 4.48, Average = 4.46

Diaphaneity:

Translucent to Opaque

Hardness:

5.5-6.5 - Knife Blade-Pyrite

Luster:

Adamantine - Metallic

Streak:

dark brown

Optical Properties of Bracewellite

Optical Data:

NCalc= 2.27 - from Gladstone-Dale relationship (KC = 0.2953) where Ncalc=Dcalc*KC+1
NCalc= 2.32 - from Gladstone-Dale relationship (KC = 0.2953) where Ncalc=Dmeas*KC+1

Calculated Properties of Bracewellite

Electron Density:

Bulk Density (Electron Density)=4.14 gm/cc
note: Specific Gravity of Bracewellite =4.29 gm/cc.

Fermion Index:

Fermion Index = 0.05
Boson Index = 0.95

Photoelectric:

PE_Bracewellite= 13.79 barns/electron
U=PE_Bracewellite x rElectron Density= 57.08 barns/cc.

Radioactivity:

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

Bracewellite Classification

Dana Class:

06.01.01.05 (06)Hydroxides and Oxides Containing Hydroxyl

(06.01)where X+++O OH

(06.01.01)Diaspore group (Orthorhombic, Pnma or Pnmd)

06.01.01.01 Diaspore AlO(OH) Pbnm 2/m 2/m 2/m

06.01.01.02 Goethite FeO(OH) Pbnm 2/m 2/m 2/m

06.01.01.03 Groutite MnO(OH) Pbnm 2/m 2/m 2/m

06.01.01.04 Montroseite (V,Fe,V)O(OH) Pbnm 2/m 2/m 2/m

06.01.01.05 Bracewellite CrO(OH) Pbnm 2/m 2/m 2/m

06.01.01.06 Tsumgallite! GaO(OH) Pbnm 2/m 2/m 2/m

Strunz Class:

04.FD.10 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.F - Hydroxides (without V or U)

04.FD -Hydroxides with OH, without H2O; chains of edge-sharing octahedra

04.FD.10 Bracewellite CrO(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Diaspore AlO(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Guyanaite CrO(OH) Pnnm 2/m 2/m 2/m

04.FD.10 Groutite MnO(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Goethite FeO(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Montroseite (V,Fe,V)O(OH) Pbnm 2/m 2/m 2/m

04.FD.10 Tsumgallite! GaO(OH) Pbnm 2/m 2/m 2/m

Other Bracewellite Information

References:

NAME( AntBidBlaNic3) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990)

See Also:

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

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

Bracewellite

Cr+++O(OH)
Dana No: 06.01.01.05 Strunz No: 04.FD.10
Locality:

Notes: