Cummingtonite Mineral Data

Advertisment

WE BUY COLLECTIONS & SINGLE IMPORTANT SPECIMENS

General Cummingtonite Information

Chemical Formula:

[ ]Mg7Si8O22(OH)2

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

Empirical Formula:

Mg₇(Si₈O₂₂)(OH)₂

Environment:

Contact and regional metamorphic rocks.

IMA Status:

Valid Species (Pre-IMA) 1824

Locality:

Cummington, Massachusetts, USA. Link to MinDat.org Location Data.

Name Origin:

Named after its locality.

Synonym:

ICSD 81355

PDF 42-545

Cummingtonite Image

Images:

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

Axial Ratios:

a:b:c =0.5229:1:0.292

Cell Dimensions:

a = 9.534, b = 18.231, c = 5.3235, Z = 2; beta = 101.97° V = 905.18 Den(Calc)= 2.86

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: C 2/m

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

By Intensity(I/I_o): 8.33(1), 2.756(0.7), 3.06(0.7),

Crystal Structure:

Mouse
drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
Keyboard
S - Stereo Pair on/off
H - Help Screen
I - Data Info
A - Atoms On/Off
P - Polyhedra On/Off
B - Bonds On/Off
Help on Above

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

Cleavage:

{110} Perfect, {???} Distinct

Color:

White, Black, Blackish brown, Blackish green, Gray.

Density:

3.1 - 3.6, Average = 3.35

Diaphaneity:

Transparent to translucent to opaque

Fracture:

Brittle - Conchoidal - Very brittle fracture producing small, conchoidal fragments.

Habit:

Columnar - Forms columns

Habit:

Fibrous - Crystals made up of fibers.

Habit:

Granular - Generally occurs as anhedral to subhedral crystals in matrix.

Hardness:

5-6 - Between Apatite and Orthoclase

Luminescence:

Non-fluorescent.

Luster:

Vitreous - Silky

Streak:

grayish white

Optical Properties of Cummingtonite

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
Ncalc = 1.6 - 1.75

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.

Pleochroism (x):

colorless, colorless, or pale yellow.

Pleochroism (y):

colorless, pale yellow, or pale brown.

Calculated Properties of Cummingtonite

Electron Density:

Bulk Density (Electron Density)=3.35 gm/cc
note: Specific Gravity of Cummingtonite =3.35 gm/cc.

Fermion Index:

Fermion Index = 0.03
Boson Index = 0.97

Photoelectric:

PE_{Cummingtonite}= 1.59 barns/electron
U=PE_{Cummingtonite} x rElectron Density= 5.33 barns/cc.

Radioactivity:

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

Cummingtonite Classification

Dana Class:

66.01.01.02 (66)Inosilicate Double-Width Unbranched Chains, W=2

(66.01)with P=2 amphibole configuration

(66.01.01)Group 1, the Mg-Fe-Mn-Li amphiboles (Monoclinic)

66.01.01.01 Magnesiocummingtonite (Mg,Fe)7Si8O22(OH)2 C 2/m 2/m

66.01.01.02 Cummingtonite []Mg7Si8O22(OH)2 C 2/m 2/m

66.01.01.03 Grunerite []Fe7Si8O22(OH)2 C 2/m 2/m

66.01.01.03b Permanganogrunerite! []Mn4(Fe)3(Si8O22)(OH)2 C 2/m 2/m

66.01.01.04 Manganocummingtonite Na(Na,Mn)2(Mg4,Fe)5Si8O22(OH)2 C 2/m 2/m

66.01.01.05 Manganogrunerite []Mn2Fe5Si8O22(OH) C 2/m 2/m

66.01.01.06 Magnesioclinoholmquistite? Li2(Mg,Fe)3Al2Si8O22(OH)2 C 2/m 2/m

66.01.01.07 Clinoholmquistite? [](Li2Mg3Al2)Si8O22(OH)2 C 2/m 2/m

66.01.01.08 Clinoferroholmquistite [](Li2Fe3Al2)Si8O22(OH)2 C 2/m 2/m

66.01.01.08a Ferri-clinoholmquistite! []Li2Mg3(Fe3)2(Si8O22)(OH)2 C 2/m 2/m

66.01.01.08b Ferri-clinoferroholmquistite! []Li2(Fe2Fe3)Si8O22(OH)2 C 2/m 2/m

66.01.01.09 Sodic-ferripedrizite! Na(LiNa)(Fe2Mg2Li)Si8O22(OH,F)2 C 2/m 2/m

66.01.01.09a Ferripedrizite! NaLi2(Fe2Mg2Li)Si8O22(OH)2 C 2/m 2/m

66.01.01.09b Sodic-ferri-ferropedrizite! NaLi2(Fe2Fe3)Si8O22(OH)2 C 2/m 2/m

66.01.01.09c Fluoro-sodic-pedrizite! NaLi2(Mg2Al2Li)S5Si8O22F2 C 2/m 2/m

Strunz Class:

09.DE.05 09 - SILICATES (Germanates)

09.D - Inosilicates* Structural terminology according to Liebau (1985)

09.DE -Inosilicates with 2-periodic double chains, Si4O11; amphibole family

09.DE.05 Ferro-anthophyllite []Fe7Si8O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Anthophyllite []Mg7Si8O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Ferrogedrite []Fe5Al2Si6Al2O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Gedrite []Mg5Al2Si6Al2O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Ferroholmquistite [](Li2Fe3Al2)Si8O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Holmquistite [](Li2Mg3Al2)Si8O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Cummingtonite []Mg7Si8O22(OH)2 C 2/m 2/m

09.DE.05 Clinoferroholmquistite [](Li2Fe3Al2)Si8O22(OH)2 C 2/m 2/m

09.DE.05 Grunerite []Fe7Si8O22(OH)2 C 2/m 2/m

09.DE.05 Magnesiocummingtonite (Mg,Fe)7Si8O22(OH)2 C 2/m 2/m

09.DE.05 Manganogrunerite []Mn2Fe5Si8O22(OH) C 2/m 2/m

09.DE.05 Magnesioanthophyllite? (Mg,Fe)7Si8O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Protomangano-ferro-anthophyllite! (Mn,Fe)2(Fe,Mg)5(Si4O11)2(OH)2 Pnmn 2/m 2/m 2/m

09.DE.05 Sodicgedrite NaMg6AlSi6Al2O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Sodic-ferro-anthophyllite! NaFe7Si8O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Sodic-ferrogedrite! NaFe6AlSi6Al2O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Sodicanthophyllite NaMg7Si8O22(OH)2 P nma 2/m 2/m 2/m

09.DE.05 Permanganogrunerite! []Mn4(Fe)3(Si8O22)(OH)2 C 2/m 2/m

09.DE.05 Protoferro-anthophyllite! (Fe,Mn)2(Fe,Mg)5(Si4O11)2(OH)2 Pnmn 2/m 2/m 2/m

09.DE.05 Fluoro-sodic-pedrizite! NaLi2(Mg2Al2Li)S5Si8O22F2 C 2/m 2/m

09.DE.05 Sodic-ferri-ferropedrizite! NaLi2(Fe2Fe3)Si8O22(OH)2 C 2/m 2/m

09.DE.05 Manganocummingtonite Na(Na,Mn)2(Mg4,Fe)5Si8O22(OH)2 C 2/m 2/m

09.DE.05 Protoanthophyllite! (Mg,Fe)7Si8O22(OH)2 Pnmn 2/m 2/m 2/m

09.DE.05 Ferri-clinoferroholmquistite! []Li2(Fe2Fe3)Si8O22(OH)2 C 2/m 2/m

09.DE.05 Sodic-ferripedrizite! Na(LiNa)(Fe2Mg2Li)Si8O22(OH,F)2 C 2/m 2/m

09.DE.05 Ferripedrizite! NaLi2(Fe2Mg2Li)Si8O22(OH)2 C 2/m 2/m

Other Cummingtonite Information

See Also:

Links to other databases for Cummingtonite :
1 - Am. Min. Crystal Structure Database
2 - Amethyst Galleries' Mineral Gallery
3 - Athena
4 - EUROmin Project
5 - Ecole des Mines de Paris
6 - Franklin Minerals(Dunn)
7 - Franklin Minerals(Palache)
8 - GeoScienceWorld
9 - Google Images
10 - Google Scholar
11 - Handbook of Mineralogy (MinSocAm)
12 - Handbook of Mineralogy (UofA)
13 - MinDAT
14 - Mineralienatlas (Deutsch)
15 - Online Mineral Museum
16 - QUT Mineral Atlas
17 - Ruff.Info
18 - Scandinavian mineral gallery
19 - UCLA - Petrography Thin-Sections
20 - WWW-MINCRYST
21 - YupRocks

Search for Cummingtonite using:

[AOL] [Bing] [Dog Pile] [GeoScienceWorld] [HotBot] [Ixquick] [Lycos] [MAMMA] [Scirus] [Teoma] [WebCrawler] [Wikipedia] [YAHOO]

Visit our Advertisers for Cummingtonite :

A Bijoux Google Search for Cummingtonite
Adam's Minerals Google Search for Cummingtonite
Cape Minerals Google Search for Cummingtonite
Dakota Matrix Minerals Google Search for Cummingtonite
Excalibur Mineral Corp. Google Search for Cummingtonite
Exceptional Minerals Google Search for Cummingtonite
John Betts Fine Minerals Search for Cummingtonite
McDougall Minerals Google Search for Cummingtonite
Mineral News Website Link
Rock and Mineral Shows Google Search for Cummingtonite
Weinrich Minerals, Inc. Google Search for Cummingtonite

Ask about Cummingtonite here :
Ask-A-Mineralogist from the Mineralogical Society of America
Mindat.org's Discussion Groups
Original Rockhounds Discussion Group
Rockhounds Discussion Group on Yahoo Groups
Mineral Discussion Forum from Fabre Minerals - also available in Español

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

Cummingtonite

[ ]Mg7Si8O22(OH)2
Dana No: 66.01.01.02 Strunz No: 09.DE.05
Locality:

Notes: