Bracewellite Mineral Data

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:

In the Bottino mine, near Seravezza, Tuscany, Italy. Link to MinDat.org Location Data.

Name Origin:

For its occurrence in the Bottino mine, Italy.

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

Diaphaniety:

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:

r_electron=4.14 gm/cc
note: r_Bracewellite=4.29 gm/cc.

Fermion Index

Fermion Index = 0.05829
Boson Index = 0.94171

Photoelectric:

PE_Bracewellite= 13.79 barns/electron
U=PE_Bracewellite x r_electron= 57.08 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Bracewellite is Not Radioactive

Bracewellite Classification

Dana Class:

6.1.1.5 (6)Hydroxides and Oxides Containing Hydroxyl

(6.1)where X+++O OH

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

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

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

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

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

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

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

Strunz Class:

IV/F.07-50 IV - Oxides

IV/F - Hydroxides and oxidic hydrates, water-bearing oxides with layered structure

IV/F.07 - Lithiophorite - Grimaldiite series

IV/F.07-10 Lithiophorite (Al,Li)MnO2(OH)2 R 3m 3 2/m

IV/F.07-20 Asbolane (Co,Ni)1-y(MnO2)2-x(OH)2-2y2x·n(H2O) Unk Hex

IV/F.07-30 Heterogenite-2H CoO(OH) P 6₃/mmc 6/m 2/m 2/m

IV/F.07-40 Heterogenite-3R CoO(OH) R 3m 3 2/m

IV/F.07-50 Bracewellite CrO(OH) Pbnm 2/m 2/m 2/m

IV/F.07-60 Guyanaite CrO(OH) Pnnm 2/m 2/m 2/m

IV/F.07-70 Grimaldiite CrO(OH) R 3m 3 2/m

Other Bracewellite Information

References:

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

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Bracewellite

Cr+++O(OH)
Dana No: 6.1.1.5 Strunz No: IV/F.07-50
Locality:

Notes: