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Coombsite Mineral Data

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General Coombsite Information

Help on Chemical  Formula: Chemical Formula: K(Mn++,Fe++,Mg)13(Si,Al)18O42(OH)14
Help on Composition: Composition: Molecular Weight = 2,127.66 gm
   Potassium   1.84 %  K     2.21 % K2O
   Magnesium   1.49 %  Mg    2.46 % MgO
   Manganese  20.14 %  Mn   26.01 % MnO
   Aluminum    5.71 %  Al   10.78 % Al2O3
   Iron       10.24 %  Fe   13.17 % FeO
   Silicon    17.82 %  Si   38.12 % SiO2
   Hydrogen    0.66 %  H     5.93 % H2O
   Oxygen     42.11 %  O
             ______        ______ 
             100.00 %       98.68 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: KMn2+7.8Fe2+3.9Mg1.3Si13.5Al4.5O42(OH)14
Help on IMA Status: IMA Status: Approved IMA 1996 (Dana # Added)
Help on Locality: Locality: Watson's Beach, Otago, South Island, New Zealand Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named for D.S Coombs of the University of Otago, New Zealand.
Help on Synonym: Synonym: IMA1989-058

Coombsite Image

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Comments: Sawed slab with brownish veining in pink (?) matrix.
Location: Watson's Beach, Otago, South Island,, New Zealand. Scale: 3x2cm x 5mm.
© Tom Loomis / Dakota Matrix

Coombsite Crystallography

Help on Axial Ratios: Axial Ratios: a:c = 1:2.46415
Help on Cell Dimensions: Cell Dimensions: a = 11.828, c = 29.146, Z = 3; V = 3,531.28 Den(Calc)= 3.00
Help on Crystal System: Crystal System: Trigonal Space Group: R 3 or R 3
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 9.68(1), 2.556(0.9), 2.793(0.7),

Physical Properties of Coombsite

Help on Cleavage: Cleavage: {???} Good
Help on Color: Color: Brown.
Help on Density: Density: 3
Help on Diaphaneity: Diaphaneity: Translucent
Help on Luster: Luster: Vitreous (Glassy)
Help on Streak: Streak: brownish yellow

Optical Properties of Coombsite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= 0.019 (Superior) - where the CI = (1-KPDmeas/KC)
CI calc= 0.019 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2032,KPDmeas= 0.2032,KC= 0.207
Ncalc = 1.62
Help on Optical Data: Optical Data: Uniaxial (-), e=1.6, w=1.619, bire=0.0190.

Calculated Properties of Coombsite

Help on Electron Density: Electron Density: Bulk Density (Electron Density)=2.93 gm/cc
note: Specific Gravity of Coombsite =3.00 gm/cc.
Help on Fermion Index: Fermion Index: Fermion Index = 0.01
Boson Index = 0.99
Help on Photoelectric: Photoelectric: PECoombsite = 9.23 barns/electron
U=PECoombsite x relectron= 27.08 barns/cc.
Help on Radioactivity: Radioactivity:

GRapi = 25.94 (Gamma Ray American Petroleum Institute Units)
Concentration of Coombsite per GRapi unit = 3.85 (%)

Estimated Radioactivity from Coombsite - barely detectable


Coombsite Classification

Help on  Dana Class: Dana Class: (74)Phyllosilicate Modulated Layers
  (74.01)with joined islands
  (74.01.04)Dana Group Zussmanite K(Fe,Mg,Mn)13[AlSi17O42](OH)14 R 3 3 Coombsite! K(Mn,Fe,Mg)13(Si,Al)18O42(OH)14 R 3 or R 3 Trig
Help on  Strunz Class: Strunz Class: 09.EG.35 09 - SILICATES (Germanates)
  09.E - Phyllosilicates
  09.EG -Double nets with 6-membered and larger rings
09.EG.35 Coombsite! K(Mn,Fe,Mg)13(Si,Al)18O42(OH)14 R 3 or R 3 Trig
09.EG.35 Zussmanite K(Fe,Mg,Mn)13[AlSi17O42](OH)14 R 3 3

Other Coombsite Information

Help on References: References: PHYS. PROP.(37th List of New Min.,Min. Mag.,1996) OPTIC PROP.(37th List of New Min.,Min. Mag.,19)
Help on See Also: See Also: Links to other databases for Coombsite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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Dana No: Strunz No: 09.EG.35





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