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General Cummingtonite Information |
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 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 | |||
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Images:
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Cummingtonite Crystallography |
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| 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 | ||
| X Ray Diffraction: |
By Intensity(I/Io): 8.33(1), 2.756(0.7), 3.06(0.7), | ||
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Crystal Structure:
Mouse |
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Physical Properties of Cummingtonite |
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| 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 |
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| 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 |
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| 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 |
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| Electron Density: |
Bulk Density (Electron Density)=3.35 gm/cc note: Specific Gravity of Cummingtonite =3.35 gm/cc. |
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| Fermion Index: |
Fermion Index = 0.03 Boson Index = 0.97 |
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| Photoelectric: |
PECummingtonite = 1.59 barns/electron U=PECummingtonite x rElectron Density= 5.33 barns/cc. |
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| Radioactivity: |
GRapi = 0 (Gamma Ray American Petroleum Institute Units) Cummingtonite is Not Radioactive |
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Cummingtonite Classification |
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| 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) | |||
| 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 | |||
Other Cummingtonite Information |
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| 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: Visit our Advertisers for Cummingtonite : A Bijoux Google Search for CummingtoniteAdam'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 : Print or Cut-and-Paste your Cummingtonite Specimen Label here :
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