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Cummingtonite

This page kindly sponsored by Bradley Ross
Formula:
☐{Mg2}{Mg5}(Si8O22)(OH)2
Cummingtonite is defined as a monoclinic amphibole belong to the magnesium-iron-manganese amphibole subgroup.
It is defined with Mg as the dominant element both in the B and C positions.
System:
Monoclinic
Colour:
Translucent dark green, ...
Lustre:
Vitreous
Hardness:
5 - 6
Name:
Cummingtonite was originally named in 1824 by Chester Dewey for the type locality in Cummington, Massachusetts, USA. Dewey (1824) did not analyze the species, but noted its unusual physical appearance. Actual physical description and chemical analyses for cummingtonite were provided by Thomson (1831) and subsequently improved by Smith and Brush (1853). Leake (1978) published a report assigning cummingtonite the wide range Mg/Mg + Fe = 0.3-0.7. In 2006, Hawthorne and Oberti published new boundaries between cummingtonite and grunerite at Mg:Fe2+ = 1:1.
Dimorph of:
Forms a series with grunerite.

Classification of Cummingtonite

Approved
9.DE.05

9 : SILICATES (Germanates)
D : Inosilicates
E : Inosilicates with 2-periodic double chains, Si4O11; Clinoamphiboles
66.1.1.1

66 : INOSILICATES Double-Width,Unbranched Chains,(W=2)
1 : Amphiboles - Mg-Fe-Mn-Li subgroup
14.21.6

14 : Silicates not Containing Aluminum
21 : Silicates of Fe and Mg
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http://www.mindat.org/min-1170.html
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Physical Properties of Cummingtonite

Vitreous
Colour:
Translucent dark green, brown, grey, colourless
Streak:
nd
Hardness (Mohs):
5 - 6
Cleavage:
Perfect
on {110}

Crystallography of Cummingtonite

Crystal System:
Monoclinic
Cell Parameters:
a = 9.53Å, b = 18.23Å, c = 5.32Å
β = 101.97°
Ratio:
a:b:c = 0.523 : 1 : 0.292
Unit Cell Volume:
V 904.16 ų (Calculated from Unit Cell)
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Data courtesy of RRUFF project at University of Arizona, used with permission.

Optical Data of Cummingtonite

Type:
Biaxial (+)
RI values:
nα = 1.639 - 1.671 nβ = 1.647 - 1.689 nγ = 1.664 - 1.708
2V:
Measured: 65° to 90°, Calculated: 70° to 90°
Max Birefringence:
δ = 0.025 - 0.037
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
r > v or r < v

Chemical Properties of Cummingtonite

Formula:
☐{Mg2}{Mg5}(Si8O22)(OH)2

Cummingtonite is defined as a monoclinic amphibole belong to the magnesium-iron-manganese amphibole subgroup.
It is defined with Mg as the dominant element both in the B and C positions.
All elements listed in formula:
Common Impurities:
Mn,Ca,Al,Ti,Na,K

Relationship of Cummingtonite to other Species

Other Members of Group:
Anthophyllite Root Name☐{X2}{Z5}(Si8O22)(OH)2
Gedrite Root Name☐{X22+}{Z32+Z23+}(Al2Si6O22)(OH)2
Grunerite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
Manganocummingtonite☐{Mn22+}{Mg5}(Si8O22)(OH)2
Manganogrunerite☐{Mn22+}{Fe52+}(Si8O22)(OH)2
Proto-ferro-suenoite☐{Mn22+}{Fe52+}(Si8O22)(OH)2
Sodic-ferro-anthophyllite{Na}{Fe22+}{Fe52+}(AlSi7O22)(OH)2
Sodic-ferrogedrite{Na}{Fe22+}{Fe32+Al2}(Al3Si5O22)(OH)2
Sodicanthophyllite{Na}{Mg2}{Mg5}(AlSi7O22)(OH)2
Sodicgedrite{Na}{Mg2}{Mg3Al2}(Al3Si5O22)(OH)2
9.DE.05Anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2
9.DE.05Clino-holmquistite Root Name☐{Li2}{Z32+Z23+}(Si8O22)(OH,F,Cl)2
9.DE.05Grunerite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
9.DE.05Manganocummingtonite☐{Mn22+}{Mg5}(Si8O22)(OH)2
9.DE.05Manganogrunerite☐{Mn22+}{Fe52+}(Si8O22)(OH)2
9.DE.05Permanganogrunerite☐{Mn22+}{Mn52+}(Si8O22)(OH)2
9.DE.05Ferro-fluoro-pedrizite{Na}{Li2}{Fe2Al2Li}(Al2Si6O22)F2
9.DE.05Ferri-fluoro-leakeite{Na}{Na2}{Mg2Fe23+Li}(Si8O22)F2
9.DE.10Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
9.DE.10Ferri-tschermakite☐{Ca2}{Mg3Fe23+}(Al2Si6O22)(OH)2
9.DE.10Ferro-actinolite☐{Ca2}{Fe52+}(Si8O22)(OH)2
9.DE.10Ferro-hornblende☐{Ca2}{Fe42+Al}(AlSi7O22)(OH)2
9.DE.10Ferro-tschermakite☐{Ca2}{Fe32+Al2}(Al2Si6O22)(OH)2
9.DE.10Joesmithite{Pb}{Ca2}{Mg3Fe23+}(Be2Si6O22)(OH)2
9.DE.10Magnesio-hornblende☐{Ca2}{Mg4Al}(AlSi7O22)(OH)2
9.DE.10Tremolite☐{Ca2}{Mg5}(Si8O22)(OH)2
9.DE.10Tschermakite☐(Ca2)(Mg3Al2)(Al2Si6O22)(OH)2
9.DE.10CannilloiteCa(Ca2)(Mg4Al)(Al3Si5O22)(OH)2
9.DE.10Fluoro-cannilloite{Ca}{Ca2}{Mg4Al}(Al3Si5O22)(F,OH)2
9.DE.10Parvo-manganotremolite☐{CaMn2+}{Mg5}(Si8O22)(OH)2
9.DE.10Fluoro-tremolite☐{Ca2}{Mg5}(Si8O22)F2
9.DE.10Potassic-fluoro-pargasite{K}{Ca2}{Mg4Al}(Al2Si6O22)F2
9.DE.15Edenite{Na}{Ca2}{Mg5}(AlSi7O22)(OH)2
9.DE.15Ferro-edenite{Na}{Ca2}{Fe52+}(AlSi7O22)(OH)2
9.DE.15Ferro-kaersutite{Na}{Ca2}{Fe32+AlTi}(Al2Si6O22)O2
9.DE.15Ferro-pargasite{Na}{Ca2}{Fe42+Al}(Al2Si6O22)(OH)2
9.DE.15Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
9.DE.15Kaersutite{Na}{Ca2}{Mg3AlTi}(Al2Si6O22)O2
9.DE.15Magnesio-hastingsite{Na}{Ca2}{Mg4Fe3+}(Al2Si6O22)(OH)2
9.DE.15Pargasite{Na}{Ca2}{Mg4Al}(Al2Si6O22)(OH)2
9.DE.15Sadanagaite{Na}{Ca2}{Mg3Al2}(Si5Al3O22)(OH)2
9.DE.15Fluoro-edenite{Na}{Ca2}{Mg5}(AlSi7O22)(F,OH)2
9.DE.15Potassic-ferro-ferri-sadanagaite{K}{Ca2}{Fe32+Fe23+}(Al3Si5O22)(OH)2
9.DE.15Potassic-sadanagaite{K}{Ca2}{Mg3Al2}(Al3Si5O22)(OH)2
9.DE.15Potassic-pargasite{K}{Ca2}{Mg4Al}(Al2Si6O22)(OH)2
9.DE.15Potassic-ferro-sadanagaite{K}{Ca2}{Fe32+Al2}(Al3Si5O22)(OH)2
9.DE.15Magnesio-fluoro-hastingsite{Na}{Ca2}{Mg4Fe3+}(Al2Si6O22)F2
9.DE.15Potassic-fluoro-hastingsite{K}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(F,OH)2
9.DE.15Potassic-chloro-hastingsite{K}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(Cl,OH)2
9.DE.15Fluoro-pargasite{Na}{Ca2}{Mg4Al}(Al2Si6O22)(F,OH)2
9.DE.15Parvo-mangano-edenite{Na}{CaMn2+}{Mg5}(AlSi7O22)(OH)2
9.DE.15Potassic-chloro-pargasite{K}{Ca2}{Mg4Al}(Al2Si6O22)(Cl,OH)2
9.DE.15Potassic-ferro-chloro-edenite{K}{Ca2}{Fe52+}(AlSi7O22)(Cl,OH)2
9.DE.15Potassic-magnesio-hastingsite{K}{Ca2}{Mg4Fe3+}(Al2Si6O22)(OH)2
9.DE.15Potassic-ferro-pargasite{K}{Ca2}{Fe42+Al}(Al2Si6O22)(OH)2
9.DE.15Chromio-pargasite{Na}{Ca2}{Mg4Cr3+}(Al2Si6O22)(OH)2
9.DE.20Ferro-taramiteNa(CaNa)(Fe32+Al2)(Al2Si6O22)(OH)2
9.DE.20Barroisite☐{CaNa}{Mg3Al2}(AlSi7O22)(OH)2
9.DE.20Ferro-ferri-barroisite☐(CaNa)(Fe32+Fe23+)(AlSi7O22)(OH)2
9.DE.20Ferro-ferri-winchite☐[CaNa][Fe42+(Fe3+,Al)]Si8O22(OH)2
9.DE.20Ferri-barroisite☐(CaNa)(Mg3Fe23+)(AlSi7O22)(OH)2
9.DE.20Ferro-ferri-taramiteNa(CaNa)(Fe32+Fe23+)(Al2Si6O22)(OH)2
9.DE.20Ferro-ferri-katophoriteNaCaNaFe42+(Fe3+)[(AlSi7)O22](OH)2
9.DE.20Ferro-barroisite☐{CaNa}{Fe32+Al2}(AlSi7O22)(OH)2
9.DE.20Ferro-richterite{Na}{CaNa}{Fe52+}(Si8O22)(OH)2
9.DE.20Ferro-winchite ☐{CaNa}{Fe42+Al}(Si8O22)(OH)2
9.DE.20Ferro-katophorite{Na}{CaNa}{Fe42+Al}[(AlSi7)O22](OH)2
9.DE.20Ferri-taramiteNa(CaNa)(Mg3Fe23+)(Al2Si6O22)(OH)2
9.DE.20Magnesiotaramite{Na}{CaNa}{Mg3AlFe3+}(Al2Si6O22)(OH)2
9.DE.20Richterite{Na}{NaCa}{Mg5}(Si8O22)(OH)2
9.DE.20Winchite☐{CaNa}{Mg4Al}(Si8O22)(OH)2
9.DE.20Taramite{Na}{CaNa}{Mg3Al2}(Al2Si6O22)(OH)2
9.DE.20Fluoro-richterite{Na}{CaNa}{Mg5}(Si8O22)(F,OH)2
9.DE.20Katophorite{Na}{CaNa}{Mg4Al}[(AlSi7)O22](OH)2
9.DE.20Potassic-fluoro-richterite{K}{CaNa}{Mg5}(Si8O22)(F,OH)2
9.DE.20Potassic-richteriteK[CaNa][Mg5]Si8O22(OH)2
9.DE.20Ferri-ghoseite☐[Mn2+Na][Mg4Fe3+]Si8O22(OH)2
9.DE.20Ferri-winchite☐[CaNa][Mg4(Fe3+,Al)]Si8O22(OH)2
9.DE.20Fluoro-taramite{Na}{CaNa}{Mg3Al2}(Al2Si6O22)F2
9.DE.25Arfvedsonite[Na][Na2][Fe42+Fe3+]Si8O22(OH)2
9.DE.25EckermanniteNaNa2(Mg4Al}Si8O22(OH)2
9.DE.25Ferro-eckermanniteNaNa2(Fe42+Al)Si8O22(OH)2
9.DE.25Ferro-glaucophane◻[Na2][Fe32+Al2]Si8O22(OH)2
9.DE.25Glaucophane◻[Na2][Mg3Al2]Si8O22(OH)2
9.DE.25Potassic-mangani-leakeite[(Na,K)][Na2][Mg2Mn23+Li]Si8O22(OH)2
9.DE.25Mangano-ferri-eckermannite[Na][Na2][Mn42+(Fe3+)]Si8O22(OH)2
9.DE.25Ferri-leakeite[Na][Na2][Mg2Fe23+Li]Si8O22(OH)2
9.DE.25Magnesio-riebeckite◻{Na2}{Mg3Fe23+}(Si8O22)(OH)2
9.DE.25Magnesio-arfvedsonite{Na}{Na2}{Mg4Fe3+}(Si8O22)(OH)2
9.DE.25NybøiteNaNa2(Mg3Al2)(AlSi7O22)(OH)2
9.DE.25Riebeckite◻[Na2][Fe32+Fe23+]Si8O22(OH)2
9.DE.25Mangano-mangani-ungarettiiteNaNa2(Mn22+Mn33+)(Si8O22)O2
9.DE.25Ferro-ferri-nybøiteNaNa2[(Fe32+,Mg)Fe23+](AlSi7O22)(OH)2
9.DE.25Clino-ferro-ferri-holmquistite◻{Li2}{Fe32+Fe23+}(Si8O22)(OH)2
9.DE.25Ferri-nybøiteNaNa2(Mg3Fe23+](AlSi7O22)(OH)2
9.DE.25Ferro-ferri-leakeite[Na][Na2][Fe22+Fe23+Li]Si8O22(OH)2
9.DE.25Ferro-ferri-fluoro-leakeiteNa(Na2)(Fe22+Fe23+Li)(Si8O22)(F)2
9.DE.25Sodic-ferri-clinoferroholmquistiteNa0.5{Li2}{Fe32+Fe23+}(Si8O22)(OH)2
9.DE.25Magnesio-fluoro-arfvedsonite[Na][Na2][Mg4Fe3+][Si8O22](F,OH)2
9.DE.25Ferri-pedrizite[Na][Li2][Mg2Fe23+Li]Si8O22(OH)2
9.DE.25Potassic-ferri-leakeite[K][Na2][Mg2Fe23+Li]Si8O22(OH)2
9.DE.25Fluoro-nybøiteNaNa2(Mg3Al2)(AlSi7O22)(F,OH)2
9.DE.25Mangani-dellaventuraite{Na}{Na2}{MgMn23+LiTi4+}Si8O22O2
9.DE.25Fluoro-pedriziteNaLi2(Mg2Al2Li)(Si8O22)F2
9.DE.25Potassic-arfvedsonite[(K,Na)][Na2][Fe42+Fe3+]Si8O22(OH)2
9.DE.25Mangani-obertiiteNa(Na2)(Mg3Mn3+Ti)(Si8O22)O2
9.DE.25Potassic-magnesio-fluoro-arfvedsonite[(K,Na)][Na2][Mg4Fe3+][Si8O22][(F,OH)2]
9.DE.25Ferro-ferri-pedrizite[Na][Li2][Fe22+Fe23+Li]Si8O22(OH)2
9.DE.25Potassic-magnesio-arfvedsonite[K][Na2][Mg4Fe3+]Si8O22(OH)2
9.DE.25PedriziteNaLi2(LiMg2Al2)(Si8O22)(OH)2
9.DE.25Ferro-pedriziteNaLi2(Fe22+Al2Li)Si8O22(OH)2
9.DE.25Fluoro-leakeiteNaNa2(Mg2Al2Li)(Si8O22)F2
9.DE.25Ferro-ferri-obertiiteNaNa2(Fe32+Fe3+Ti)Si8O22O2
14.21.1Olivine(Mg,Fe2+)2SiO4
14.21.2Ringwoodite(Mg,Fe2+)2SiO4
14.21.3Wadsleyite(Mg,Fe2+)2(SiO4)
14.21.4ClinoferrosiliteFe2+SiO3
14.21.5Anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2
14.21.7 Magnesiocummingtonite
14.21.8Grunerite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
14.21.9MinnesotaiteFe32+Si4O10(OH)2
14.21.10Chesterite(Mg,Fe)17Si20O54(OH)6
14.21.11Jimthompsonite(Mg,Fe)5Si6O16(OH)2
14.21.12Clinojimthompsonite(Mg,Fe)5Si6O16(OH)2
14.21.13MajoriteMg3(Fe2+,Si,Al)2(SiO4)3
14.21.14Balangeroite(Mg,Fe2+,Fe3+,Mn2+)42Si16O54(OH)40

Other Names for Cummingtonite

Other Information

Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Cummingtonite

Reference List:
Dewey, C. (1824) A Sketch of the Geology and Mineralogy of the Western Part of Massachusetts, and a Small Part of Adjoining States. American Journal of Science, first series: 8, 1-60.

Thomson, T. (1831) (paper read March 17, 1828) Account of the Constituents of various Minerals. 2. Cummingtonite. Transactions of the Royal Society of Edinburgh: 11: 244-248.

Smith, J.L. Brush, G.J. (1853) Re-examination of American Minerals... 20. Cummingtonite – a Hornblende. American Journal of Science, second series: 16: 48-49.

Larsen, E.S. (1942) Alkalic Rocks of Iron Hill, Gunnison County, Colorado. USGS Professional Paper 197-A: 12-13.

Klein, U., Sharp, T.G., Schumacher, J,C. (1997) Analytical Electron Microscopy on Nanometer-scale hornblende lamellae: Low-temperature Exsolution in Cummingtonite. American Mineralogist: 82: 1079-1090.

Mandarino, J.A. (1998) The Second List of Additions and Corrections to the Glossary of Mineral Species (1995). The Amphibole Group. Mineralogical Record: 29: 169-174.

Yang, H., Hazen, R.M., Prewitt, C.T., Finger, L.W., Lu, R., Hemley, R.J. (1998) High-pressure single-crystal X-ray diffraction and infrared spectroscopic studies of the C2/m-P2 1/m phase transition in cummingtonite. American Mineralogist: 83: 288-299.

Boffa Ballaran, T., Angel, R.J., Carpenter, M.A. (2000) High-pressure transformation behaviour of the cummingtonite-grunerite solid solution. European Journal of Mineralogy: 12: 1195-1213.

Boffa Ballaran, T., Carpenter, M.A., Domeneghetti, M.C. (2001) Phase transition and mixing behavior of the cummingtonite-grunerite solid solution. Physics and Chemistry of Minerals: 28: 87-101.

Boffa Ballaran, T., Carpenter, M.A., Domeneghetti, M.C. (2004) Order parameter variation through the P2 1/m - C2/m phase transition in cummingtonite. American Mineralogist: 89: 1717-1727.

Hawthorne, F.C., Oberti, R. (2006) On the classification of amphiboles. The Canadian Mineralogist: 44: 1-21.

Hawthorne, F.C., Oberti, R., Harlow, G.E., Maresch, W.V., Martin, R.F., Schumacher, J.C., Welch, M.D. (2012) Nomenclature of the amphibole supergroup. American Mineralogist: 97: 2031-2048.

Internet Links for Cummingtonite

Localities for Cummingtonite

map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
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