Woodallite Mineral Data

General Woodallite Information

Chemical Formula:

Mg6Cr2(OH)16Cl2•4(H2O)

Composition:

Molecular Weight = 659.31 gm

Magnesium 22.86 % Mg 37.90 % MgO

Aluminum 0.82 % Al 1.55 % Al₂O₃

Chromium 9.46 % Cr 13.83 % Cr₂O₃

Iron 4.24 % Fe 6.06 % Fe₂O₃

Hydrogen 3.67 % H 32.79 % H₂O

Carbon 0.36 % C 1.34 % CO₂

Chlorine 8.60 % Cl 8.60 % Cl

- % Cl -1.94 % -O=Cl₂

Oxygen 49.99 % O

______ ______

100.00 % 100.12 % = TOTAL OXIDE

Empirical Formula:

Mg_6.2Cr_1.2Fe³⁺_0.5Al_0.2(OH)₁₆Cl_1.6(CO₃)_0.2ï¿½4(H₂O)

Environment:

Altered dunite associated with Cr minerals.

IMA Status:

Approved IMA 2000 (Dana # Added)

Locality:

Mount Keith nickel deposit, 90 km NNE of Leinster, Western Australia. Link to MinDat.org Location Data.

Name Origin:

Named for Roy Woodall (1930-), Australian geologist.

Synonym:

IMA2000-042

Woodallite Crystallography

Axial Ratios:

a:c = 1:7.77022

Cell Dimensions:

a = 3.103, c = 24.111, Z = 0.375; V = 201.05 Den(Calc)= 2.04

Crystal System:

Trigonal - Hexagonal Scalenohedral H-M Symbol (3 2/m) Space Group: R 3m

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

By Intensity(I/I_o): 8.04(1)(003), 2.0072(0.6)(0.1.12), 4.0205(0.48)(006),2.624(0.3), 2.3488(0.05)(015),

Physical Properties of Woodallite

Cleavage:

{001} Perfect

Color:

Deep magenta, Purple.

Density:

2.062

Diaphaneity:

Transparent

Fracture:

Brittle - Sectile - Brittle fracture with slightly sectile shavings possible.

Habit:

Platy - Sheet forms (e.g. micas).

Hardness:

1.5-2 - Talc-Gypsum

Luster:

Resinous - Waxy

Streak:

pale pinkish white

Optical Properties of Woodallite

Gladstone-Dale:

CI meas= 0.055 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= 0.045 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2672,KPDmeas= 0.2643,KC= 0.2797
Ncalc = 1.57 - 1.58

Optical Data:

Uniaxial (-), e=1.535, w=1.555, bire=0.0200.

Calculated Properties of Woodallite

Electron Density:

Bulk Density (Electron Density)=2.08 gm/cc
note: Specific Gravity of Woodallite =2.04 gm/cc.

Fermion Index:

Fermion Index = 0.03
Boson Index = 0.97

Photoelectric:

PE_Woodallite= 4.40 barns/electron
U=PE_Woodallite x rElectron Density= 9.15 barns/cc.

Radioactivity:

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

Woodallite Classification

Dana Class:

06.04.05.02 (06)Hydroxides and Oxides Containing Hydroxyl

(06.04)containing multiple cations

(06.04.05)Dana Group

06.04.05.01 Iowaite Mg4Fe(OH)8OCl•2-4(H2O) R 3m 3 2/m

06.04.05.02 Woodallite! Mg6Cr2(OH)16Cl2•4(H2O) R 3m 3 2/m

Strunz Class:

04.FL.05 04 - OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodate

04.F - Hydroxides (without V or U)

04.FL -Hydroxides with H2O ï¿½ (OH); sheets of edge-sharing octahedra

04.FL.05 Akdalaite 5(Al2O3)•(H2O) P 6₃mc 6mm

04.FL.05 Meixnerite Mg6Al2(OH)18•4(H2O) R 3m 3 2/m

04.FL.05 Jamborite (Ni,Ni,Fe)(OH)2(OH,S,(H2O)) Unk Hex

04.FL.05 Iowaite Mg4Fe(OH)8OCl•2-4(H2O) R 3m 3 2/m

04.FL.05 Muskoxite Mg7Fe4O13•10(H2O) Unk (pseudo HEX-R) Trig

04.FL.05 Woodallite! Mg6Cr2(OH)16Cl2•4(H2O) R 3m 3 2/m

Other Woodallite Information

References:

NAME( AmMin, Vol 87, p 182) PHYS. PROP.(AmMin, Vol 87, p 182) OPTIC PROP.(AmMin, Vol 87, p 182)

See Also:

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

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

Woodallite

Mg6Cr2(OH)16Cl2•4(H2O)
Dana No: 06.04.05.02 Strunz No: 04.FL.05
Locality:

Notes:

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