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Antigorite

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Formula:
Mg3(Si2O5)(OH)4
System:
Monoclinic
Colour:
green, green-blue, ...
Hardness:
3½ - 4
Name:
Named in 1840 by Mathias Eduard Schweizer for the type locality, Valle di Antigorio, Domodossola, Piedmont, Italy, although there is a small question if he were on the Italian side of the border.
The type material was collected near the border between Switzerland and Italy from outcrops of the Geisspfad serpentinite. It is not clear in which country the material was sampled.

Kaolinite-Serpentine group.

m = 16 and m = 17 polysomes known.

See also the closely related chrysotile and lizardite.

Note: Antigorite is not the most common serpentine, although it is a common member of the group. Volumetrically, lizardite is the most abundant sepentine.

Visit gemdat.org for gemological information about Antigorite.

Classification of Antigorite

Approved
9.ED.15

9 : SILICATES (Germanates)
E : Phyllosilicates
D : Phyllosilicates with kaolinite layers composed of tetrahedral and octahedral nets
71.1.2a.1

71 : PHYLLOSILICATES Sheets of Six-Membered Rings
1 : Sheets of 6-membered rings with 1:1 layers
14.4.15

14 : Silicates not Containing Aluminum
4 : Silicates of Mg
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Type Occurrence of Antigorite

General Appearance of Type Material:
massive, scales, plates
Place of Conservation of Type Material:
ETH Zürich, Switzerland
Year of Discovery:
1840
Geological Setting of Type Material:
Serpentinite
Associated Minerals at Type Locality:

Physical Properties of Antigorite

Vitreous
Diaphaneity (Transparency):
Transparent
Colour:
green, green-blue, white, brown, black
Streak:
greenish white
Hardness (Mohs):
3½ - 4
Cleavage:
Distinct/Good
[001] good
Fracture:
Splintery
Density:
2.5 - 2.6 g/cm3 (Measured)    2.52 g/cm3 (Calculated)

Crystallography of Antigorite

Crystal System:
Monoclinic
Class (H-M):
m - Domatic
Space Group:
Bm
Cell Parameters:
a = 43.53Å, b = 9.25Å, c = 7.26Å
β = 91.13°
Ratio:
a:b:c = 4.706 : 1 : 0.785
Unit Cell Volume:
V 2,922.69 ų (Calculated from Unit Cell)
X-Ray Powder Diffraction Data:
d-spacingIntensity
7.28 (100)
7.21 (10)
3.623 (60)
3.589 (10)
2.523 (30)
2.169 (10)
2.150 (10)
1.558 (10)

Optical Data of Antigorite

Type:
Biaxial (-)
RI values:
nα = 1.555 - 1.567 nβ = 1.560 - 1.573 nγ = 1.560 - 1.573
2V:
Measured: 20° to 50°
Max Birefringence:
δ = 0.005 - 0.006
Image shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:
Low
Dispersion:
weak

Chemical Properties of Antigorite

Formula:
Mg3(Si2O5)(OH)4
Essential elements:
All elements listed in formula:
Common Impurities:
Ni,Al,Mn

Relationship of Antigorite to other Species

Other Members of Group:
AmesiteMg2Al(AlSiO5)(OH)4
Baumite(Mg,Al,Mn,Zn,Fe)3(Si,Al)2O5(OH)4
Berthierine(Fe2+,Fe3+,Al)3(Si,Al)2O5(OH)4
Brindleyite(Ni,Al)3(Si,Al)2O5(OH)4
Caryopilite(Mn,Mg)3(Si2O5)(OH)4
ChrysotileMg3(Si2O5)(OH)4
Clinochrysotile
CronstedtiteFe22+Fe3+((Si,Fe3+)2O5)(OH)4
DickiteAl2(Si2O5)(OH)4
Fraipontite(Zn,Al)3((Si,Al)2O5)(OH)4
GreenaliteFe2-3(Si2O5)(OH)4
HalloysiteAl2(Si2O5)(OH)4
KaoliniteAl2(Si2O5)(OH)4
KellyiteMn22+Al(AlSiO5)(OH)4
LizarditeMg3(Si2O5)(OH)4
ManandoniteLi2Al4(Si2AlB)O10(OH)8
NacriteAl2(Si2O5)(OH)4
Népouite(Ni,Mg)3(Si2O5)(OH)4
Odinite(Fe,Mg,Al,Fe,Ti,Mn)2.4((Si,Al)2O5)(OH)4
Orthochrysotile
Parachrysotile
PecoraiteNi3(Si2O5)(OH)4
Webskyite
9.ED.05DickiteAl2(Si2O5)(OH)4
9.ED.05KaoliniteAl2(Si2O5)(OH)4
9.ED.05NacriteAl2(Si2O5)(OH)4
9.ED.05Odinite(Fe,Mg,Al,Fe,Ti,Mn)2.4((Si,Al)2O5)(OH)4
9.ED.10HalloysiteAl2(Si2O5)(OH)4
9.ED.10HisingeriteFe23+(Si2O5)(OH)4 · 2H2O
9.ED.10Halloysite-7ÅAl2(Si2O5)(OH)4
9.ED.15AmesiteMg2Al(AlSiO5)(OH)4
9.ED.15Berthierine(Fe2+,Fe3+,Al)3(Si,Al)2O5(OH)4
9.ED.15Brindleyite(Ni,Al)3(Si,Al)2O5(OH)4
9.ED.15Caryopilite(Mn,Mg)3(Si2O5)(OH)4
9.ED.15ChrysotileMg3(Si2O5)(OH)4
9.ED.15CronstedtiteFe22+Fe3+((Si,Fe3+)2O5)(OH)4
9.ED.15Fraipontite(Zn,Al)3((Si,Al)2O5)(OH)4
9.ED.15GreenaliteFe2-3(Si2O5)(OH)4
9.ED.15KellyiteMn22+Al(AlSiO5)(OH)4
9.ED.15LizarditeMg3(Si2O5)(OH)4
9.ED.15ManandoniteLi2Al4(Si2AlB)O10(OH)8
9.ED.15Népouite(Ni,Mg)3(Si2O5)(OH)4
9.ED.15PecoraiteNi3(Si2O5)(OH)4
9.ED.15GuidottiiteMn2Fe3+(Fe3+SiO5)(OH)4
9.ED.20Allophane(Al2O3)(SiO2)1.3-2 · 2.5-3H2O
9.ED.20ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O (x < 1)
9.ED.20ImogoliteAl2SiO3(OH)4
9.ED.20Neotocite(Mn,Fe,Mg)SiO3 · H2O
9.ED.25BismutoferriteFe23+Bi(SiO4)2(OH)
9.ED.25ChapmaniteFe23+Sb3+(Si2O5)O3(OH)
14.4.1ForsteriteMg2SiO4
14.4.2EnstatiteMgSiO3
14.4.3ClinoenstatiteMgSiO3
14.4.4ChrysotileMg3(Si2O5)(OH)4
14.4.5Clinochrysotile
14.4.6Orthochrysotile
14.4.7Parachrysotile
14.4.8LizarditeMg3(Si2O5)(OH)4
14.4.9TalcMg3(Si4O10)(OH)2
14.4.10SpadaiteMgSiO2(OH)2 · H2O (?)
14.4.11SepioliteMg4(Si6O15)(OH)2 · 6H2O
14.4.12LoughliniteNa2Mg3Si6O16 · 8H2O
14.4.13EifeliteKNa3Mg4Si12O30
14.4.14Stevensite(Ca,Na)xMg3-x(Si4O10)(OH)2
14.4.16 Magnesio-anthophyllite

Other Names for Antigorite

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 Antigorite

Reference List:
Zussman, J. (1954): Investigation of the crystal structure of antigorite. Mineralogical Magazine: 30: 498-512.

Kunze, V.G. (1958): Die gewellte Struktur des Antigorits, II. Zeitschrift für Kristallographie: 110: 282-320.

Kunze, V.G. (1961): Antigorit. Fortschritte der Mineralogie: 39: 206-324.

Spinnler, G.E. (1985): HRTEM study of antigorite, pyroxene-serpentine reactions and chlorite, 248 p. PhD Thesis, Arizona State University, Tempe, Arizona.

Uehara, S. and Shirozu, H. (1985): Variations in chemical composition and structural properties of antigorites. Mineralogical Journal: 12: 299-318.

Mellini, M., Trommsdorff, V., and Compagnoni, R. (1987): Antigorite polysomatism: Behaviour during progressive metamorphism. Contributions to Mineralogy and Petrology: 97: 147-155.

Otten, M.T. (1993): High-resolution electron microscopy of polysomatism and stacking defects in antigorite. American Mineralogist: 78: 75-84.

Viti, C. and Mellini, M. (1996): Vein antigorite from Elba Island, Italy. European Journal of Mineralogy: 8: 423-434.

Wunder, B. and Schreyer, W. (1997): Antigorite: high-pressure stability in the system MgO-SiO2-H2O. Lithos: 41: 213-227.

Wunder, B., Baronnet, A., and Schreyer, W. (1997): Ab-initio synthesis and TEM confirmation of antigorite in the system MgO-SiO2-H2O. American Mineralogist: 82: 760-764.

Uehara, S. (1998): TEM and XRD study of antigorite superstructures. Canadian Mineralogist: 36: 1595-1605.

Wunder, B., Wirth, R., and Gottschalk, M. (2001): Antigorite: Pressure and temperature dependence of polysomatism and water content. European Journal of Mineralogy: 13: 485-495.

Dodony, I., Posfai, M., and Buseck, P.R. (2002): Revised structure models for antigorite: An HRTEM study. American Mineralogist: 87: 1443-1457.

Bromiley, G.D. and Pawley, A.R. (2003): The stability of antigorite in the systems MgO-SiO2-H2O (MSH) and MgO-Al2O3-SiO2-H2O (MASH): The effects of Al 3+ substitution on high-pressure stability. American Mineralogist: 88: 99-108.

Grobéty, B. (2003): Polytypes and higher-order structures of antigorite A TEM study. American Mineralogist: 88: 27-36.

Capitani, G.C. and Mellini, M. (2004): The modulated crystal structure of antigorite: the m = 17 polysome. American Mineralogist: 89: 147-158.

Capitani, G.C. and Mellini, M. (2005): HRTEM evidence for 8-reversals in the m = 17 antigorite polysome. American Mineralogist: 90: 991-999.

Capitani, G.C. and Mellini, M. (2006): The crystal structure of a second antigorite polysome (m = 16), by single-crystal synchrotron diffraction. American Mineralogist: 91: 394-399.

Internet Links for Antigorite

Localities for Antigorite

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.
Mineral and/or Locality  
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