Cummingtonite Mineral Data

General Cummingtonite Information
Help on Chemical Formula: Chemical Formula: [ ]Mg7Si8O22(OH)2
Help on Composition: Composition: Molecular Weight = 780.82 gm
   Magnesium  21.79 %  Mg   36.13 % MgO
   Silicon    28.78 %  Si   61.56 % SiO2
   Hydrogen    0.26 %  H     2.31 % H2O
   Oxygen     49.18 %  O
             ______        ______ 
             100.00 %      100.00 % = TOTAL OXIDE
Help on Empirical Formula: Empirical Formula: Mg7(Si8O22)(OH)2
Help on Environment: Environment: Contact and regional metamorphic rocks.
Help on IMA Status: IMA Status: Valid Species (Pre-IMA) 1824
Help on Locality: Locality: Cummington, Massachusetts, USA. Link to MinDat.org Location Data.
Help on Name Origin: Name Origin: Named after its locality.
Help on Synonym: Synonym: ICSD 81355
  PDF 42-545
 

Cummingtonite Image

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Cummingtonite

Comments: Light brown prismatic crystalline aggregate of cummingtonite with radiating structure.
Location: West Chesterfield, Hampshire County, Massachusetts, USA. Scale: See Photo.
© Jeff Weissman / Photographic Guide to Mineral Species

Cummingtonite Crystallography
Help on Axial Ratios: Axial Ratios: a:b:c =0.5229:1:0.292
Help on Cell Dimensions: Cell Dimensions: a = 9.534, b = 18.231, c = 5.3235, Z = 2; beta = 101.97° V = 905.18 Den(Calc)= 2.86
Help on Crystal System: Crystal System: Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/m
Help on X Ray Diffraction: X Ray Diffraction: By Intensity(I/Io): 8.33(1), 2.756(0.7), 3.06(0.7),
Click Here for Large Cummingtonite Structure Window Crystal Structure:

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Fischer K F , American Mineralogist , 51 (1966) p.814-818, A further refinement of the crystal structure of cummingtonite, (Mg,Fe)7(Si4O11)2(OH)2

View Additional jPOWD Structure files for Cummingtonite
[1] [10] [11] [12] [13] [2] [3] [4] [5] [6] [7] [8] [9]
 

Physical Properties of Cummingtonite

Help on Cleavage: Cleavage: [110] Perfect, [???] Distinct
Help on Color: Color: White, Black, Blackish brown, Blackish green, Gray.
Help on Density: Density: 3.1 - 3.6, Average = 3.35
Help on Diaphaniety: Diaphaniety: Transparent to translucent to opaque
Help on Fracture: Fracture: Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.
Help on Habit: Habit: Columnar - Forms columns
Help on Habit: Habit: Fibrous - Crystals made up of fibers.
Help on Habit: Habit: Granular - Generally occurs as anhedral to subhedral crystals in matrix.
Help on Hardness: Hardness: 5-6 - Between Apatite and Orthoclase
Help on Luminescence: Luminescence: Non-fluorescent.
Help on Luster: Luster: Vitreous - Silky
Help on Streak: Streak: grayish white
 

Optical Properties of Cummingtonite

Help on Gladstone-Dale: Gladstone-Dale: CI meas= 0.04 (Good) - where the CI = (1-KPDmeas/KC)
CI calc= -0.125 (Poor) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2341,KPDmeas= 0.1999,KC= 0.2082
Help on Optical Data: Optical Data: Biaxial (+), a=1.639-1.671, b=1.647-1.689, g=1.664-1.708, bire=0.0250-0.0370, 2V(Calc)=70-90, 2V(Meas)=65-90. Dispersion r > v or r < v.
Help on Pleochroism (x): Pleochroism (x): colorless, colorless, or pale yellow.
Help on Pleochroism (y): Pleochroism (y): colorless, pale yellow, or pale brown.
Help on Pleochroism (z): Pleochroism (z): colorless, pale greenish yellow, or pale violet.
 

Calculated Properties of Cummingtonite

Help on Electron Density: Electron Density:

relectron=3.35 gm/cc
note: rCummingtonite =3.35 gm/cc.
Help on Fermion Index Fermion Index Fermion Index = 0.03546
Boson Index = 0.96454
Help on Photoelectric: Photoelectric:

PECummingtonite = 1.59 barns/electron
U=PECummingtonite x relectron= 5.33 barns/cc.
Help on Radioactivity: Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Cummingtonite is Not Radioactive
 

Cummingtonite Classification
Help on Dana Class: Dana Class: 66.1.1.2 (66)Inosilicate Double-Width Unbranched Chains, W=2
  (66.1)Dana Type
  (66.1.1)Group 1, the Mg-Fe-Mn-Li amphiboles (Monoclinic)
 
66.1.1.1 Magnesiocummingtonite (Mg,Fe)7Si8O22(OH)2 C 2/m 2/m
 
66.1.1.2 Cummingtonite []Mg7Si8O22(OH)2 C 2/m 2/m
 
66.1.1.3 Grunerite []Fe7Si8O22(OH)2 C 2/m 2/m
 
66.1.1.3b Permanganogrunerite! []Mn4(Fe)3(Si8O22)(OH)2 C 2/m 2/m
 
66.1.1.4 Manganocummingtonite Na(Na,Mn)2(Mg4,Fe)5Si8O22(OH)2 C 2/m 2/m
 
66.1.1.5 Manganogrunerite []Mn2Fe5Si8O22(OH) C 2/m 2/m
 
66.1.1.6 Magnesioclinoholmquistite? Li2(Mg,Fe)3Al2Si8O22(OH)2 C 2/m 2/m
 
66.1.1.7 Clinoholmquistite? [](Li2Mg3Al2)Si8O22(OH)2 C 2/m 2/m
 
66.1.1.8 Clinoferroholmquistite [](Li2Fe3Al2)Si8O22(OH)2 C 2/m 2/m
 
66.1.1.8a Ferri-clinoholmquistite! []Li2Mg3(Fe3)2(Si8O22)(OH)2 C 2/m 2/m
 
66.1.1.8b Ferri-clinoferroholmquistite! []Li2(Fe2Fe3)Si8O22(OH)2 C 2/m 2/m
 
66.1.1.9 Sodic-ferripedrizite! Na(LiNa)(Fe2Mg2Li)Si8O22(OH,F)2 C 2/m 2/m
 
66.1.1.9a Ferripedrizite! NaLi2(Fe2Mg2Li)Si8O22(OH)2 C 2/m 2/m
 
66.1.1.9b Sodic-ferri-ferropedrizite! NaLi2(Fe2Fe3)Si8O22(OH)2 C 2/m 2/m
 
66.1.1.9c Fluoro-sodic-pedrizite! NaLi2(Mg2Al2Li)S5Si8O22F2 C 2/m 2/m
Help on Strunz Class: Strunz Class: VIII/F.07-20 VIII - Silicates
  VIII/F - Inosilicates (chain and band) double chains [Si4O11]6- , Mg-Fe-Mn-Amphiboles
  VIII/F.07 - Amphibole group, Magnesiocummingtonite - Ferroclinoholmquistite series
 
VIII/F.07-10 Magnesiocummingtonite (Mg,Fe)7Si8O22(OH)2 C 2/m 2/m
 
VIII/F.07-20 Cummingtonite []Mg7Si8O22(OH)2 C 2/m 2/m
 
VIII/F.07-30 Grunerite []Fe7Si8O22(OH)2 C 2/m 2/m
 
VIII/F.07-40 Manganocummingtonite Na(Na,Mn)2(Mg4,Fe)5Si8O22(OH)2 C 2/m 2/m
 
VIII/F.07-50 Manganogrunerite []Mn2Fe5Si8O22(OH) C 2/m 2/m
 
VIII/F.07-55 Permanganogrunerite! []Mn4(Fe)3(Si8O22)(OH)2 C 2/m 2/m
 
VIII/F.07-60 Magnesioclinoholmquistite? Li2(Mg,Fe)3Al2Si8O22(OH)2 C 2/m 2/m
 
VIII/F.07-70 Clinoholmquistite? [](Li2Mg3Al2)Si8O22(OH)2 C 2/m 2/m
 
VIII/F.07-80 Clinoferroholmquistite [](Li2Fe3Al2)Si8O22(OH)2 C 2/m 2/m
 
VIII/F.07-90 Ferri-clinoferroholmquistite! []Li2(Fe2Fe3)Si8O22(OH)2 C 2/m 2/m
 

Other Cummingtonite Information
Help on References: References: NAME( Duda&Rejl90) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(Heinrich65)
Help on See Also: See Also: Links to other databases for Cummingtonite :
1 -Am. Min. Crystal Structure Database 2 - Amethyst Galleries' Mineral Gallery 3 - Applied Mineralogy 4 -Athena 5 - Crocoite.com Mineral Locations 6 - EUROmin Project 7 - Franklin Minerals(Dunn) 8 - Franklin Minerals(Palache) 9 -Google Images 10 -Google Scholar 11 -Handbook of Mineralogy (MinSocAm) 12 -Handbook of Mineralogy (UofA) 13 -MinDAT 14 -MinMax(Deutsch) 15 -MinMax(English) 16 -Mineralienatlas (Deutsch) 17 - Minerals of Wisconsin 18 -QUT Mineral Atlas 19 - Scandinavian mineral gallery 20 - UCLA - Petrography Thin-Sections 21 - WWW-MINCRYST 22 - YupRocks 23 -École des Mines de Paris

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Cummingtonite

[ ]Mg7Si8O22(OH)2
Dana No: 66.1.1.2 Strunz No: VIII/F.07-20
Locality:

 

Notes:

 
 
   
 
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