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Sillimanite

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Formula:
Al
 
2
(SiO
 
4
)O
System:OrthorhombicColour:Colorless, white, ...
Hardness:6½ - 7½
Name:
Named by George Thomas Bowen in 1824 in honor of Benjamin Silliman, Sr. [August 8, 1779 North Stratford(Trumbull), Connecticut, USA - November 24, 1864 New Haven, Connecticut, USA], Professor of Chemistry and Geology, Yale University, New Haven, Connecticut, USA, and founder of the American Journal of Science (Silliman's Journal).
Polymorph of:Andalusite, Kyanite


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Classification of Sillimanite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:8/B.02-10
Nickel-Strunz 10th (pending) edition ID:9.AF.05

9 : SILICATES (Germanates)
A : Nesosilicates
F : Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination
Dana 8th edition ID:52.2.2a.1

52 : NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
2 : Insular SiO4 Groups and O, OH, F, and H2O with cations in [4] and >[4] coordination
Hey's CIM Ref.:15.3

15 : Silicates of Aluminum
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Type Occurrence of Sillimanite

Type Locality:Chester, Middlesex Co., Connecticut, USA
General Appearance of Type Material:White to lightly yellow stained fibers in biotite schist with quartz segregations.
Year of Discovery:1824
Geological Setting of type material:Metasedimentary rocks
Associated Minerals at type locality:
QuartzBiotite

Occurrences of Sillimanite

Geological Setting:High pressure and high temperature thermal aureoles around intrusive rocks. Similar conditions in regionally metamorphosed rocks.

Physical Properties of Sillimanite

Lustre:Sub-Vitreous, Greasy, Silky
Diaphaneity (Transparency):Transparent, Translucent
Colour:Colorless, white, yellow, brown, green, gray.
Comment:Ideally colorless, inclusions and stains are responsible for other colors.
Streak:white
Hardness (Mohs):6½ - 7½
Tenacity:Brittle
Cleavage:Perfect
{010} perfect
Fracture:Irregular/Uneven
Comment:Usually fibrous due to breakage along fiber boundaries.
Density (measured):3.23 - 3.27 g/cm3
Density (calculated):3.24 g/cm3

Crystallography of Sillimanite

Crystal System:Orthorhombic
Class (H-M):mmm (2/m 2/m 2/m) - Dipyramidal
Cell Parameters:a = 7.484Å, b = 7.672Å, c = 5.770Å
Ratio:a:b:c = 0.975 : 1 : 0.752
Unit Cell Volume:V 331.30 ų (Calculated from Unit Cell)
Z:4
Morphology:Usually fibrous in wavy bundles. Rarely in well defined rectangular to square cross-sectioned prisms.
Comment:Pbnm
X-Ray Powder Diffraction:
Image Loading

Radiation - Copper Kα
Data Set:
Horizontal Axis: ° to ° Vertical Axis: % Source Data: Filtered Data:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction:
d-spacingIntensity
3.84 (10)
3.42 (100)
3.37 (40)
2.68 (20)
2.54 (20)
2.42 (20)
2.20 (30)
1.520 (10)
Comments:ICDD 38-471

Optical Data of Sillimanite

Type:Biaxial (+)
RI values: nα = 1.653 - 1.661 nβ = 1.654 - 1.670 nγ = 1.669 - 1.684
2V:Measured: 20° to 30°, Calculated: 30° to 80°
Birefringence:0.016
Maximum Birefringence:δ = 0.016 - 0.023

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Moderate
Dispersion:r > v strong
Optical Extinction:Parallel. XYZ=abc
Pleochroism:Weak
Comments:May be seen in colored varieties, but only in thick sections. X=pale yellow Y=brown or light green Z=dark brown or blue

Chemical Properties of Sillimanite

Formula:
Al
 
2
(SiO
 
4
)O
Simplified for copy/paste:Al2(SiO4)O
Essential elements:Al, O, Si
All elements listed in formula:Al, O, Si
Common Impurities:Fe

Relationship of Sillimanite to other Species

Common Associates:
QuartzMuscoviteBiotite
Related Minerals - Nickel-Strunz Grouping):

- +
9.AF.10Andalusite
Al
 
2
(SiO
 
4
)O
9.AF.10Kanonaite
Mn
3+
 
Al(SiO
 
4
)O
9.AF.15Kyanite
Al
 
2
(SiO
 
4
)O
9.AF.20Mullite
Al
 
4+2x
Si
 
2-2x
O
 
10-x
9.AF.20Krieselite
(Al,Ga)
 
2
(GeO
 
4
)(OH)
 
2
9.AF.23Boromullite
Al
 
9
BSi
 
2
O
 
19
9.AF.25Yoderite
Mg(Al,Fe
3+
 
)
 
3
(SiO
 
4
)
 
2
O(OH)
9.AF.30Magnesiostaurolite
(Mg,Li,Fe
2+
 
)
 
1.5-2
Al
 
9
(SiO
 
4
)
 
4
O
 
6
(OH)
 
2
9.AF.30Staurolite
(Fe
2+
 
,Mg,Zn)
 
1.5-2
Al
 
9
(SiO
 
4
)
 
4
O
 
6
(OH,O)
 
2
9.AF.30Zincostaurolite
(Zn,Li,Fe
2+
 
,Mg)
 
1.5-2
Al
 
9
(SiO
 
4
)
 
4
O
 
6
(OH)
 
2
9.AF.35Topaz
Al
 
2
(SiO
 
4
)(F,OH)
 
2
9.AF.40Norbergite
Mg
 
3
(SiO
 
4
)(F,OH)
 
2
9.AF.45Alleghanyite
Mn
2+
5
(SiO
 
4
)
 
2
(OH)
 
2
9.AF.45Chondrodite
(Mg,Fe
2+
 
)
 
5
(SiO
 
4
)
 
2
(F,OH)
 
2
9.AF.45Reinhardbraunsite
Ca
 
5
(SiO
 
4
)
 
2
(OH,F)
 
2
9.AF.45Kumtyubeite
Ca
 
5
(SiO
 
4
)
 
2
F
 
2
9.AF.45Hydroxylchondrodite
Mg
 
5
(SiO
 
4
)
 
2
(OH)
 
2
9.AF.50Humite
(Mg,Fe
2+
 
)
 
7
(SiO
 
4
)
 
3
(F,OH)
 
2
9.AF.50Manganhumite
(Mn
2+
 
,Mg)
 
7
(SiO
 
4
)
 
3
(OH)
 
2
9.AF.50Unnamed (Ca-analogue of Humite)
Ca
 
7
(SiO
 
4
)
 
4
F
 
2
9.AF.55Clinohumite
Mg
 
9
(SiO
 
4
)
 
4
F
 
2
9.AF.55Sonolite
Mn
2+
9
(SiO
 
4
)
 
4
(OH,F)
 
2
9.AF.55Hydroxylclinohumite
Mg
 
9
(SiO
 
4
)
 
4
(OH)
 
2
9.AF.60Leucophoenicite
Mn
2+
7
(SiO
 
4
)
 
3
(OH)
 
2
9.AF.65Ribbeite
(Mn
2+
 
,Mg)
 
5
(SiO
 
4
)
 
2
(OH)
 
2
9.AF.70Jerrygibbsite
Mn
2+
9
(SiO
 
4
)
 
4
(OH)
 
2
9.AF.75Franciscanite
Mn
2+
6
(V
5+
 
,☐)
 
2
(SiO
 
4
)
 
2
(O,OH)
 
6
9.AF.75Örebroite
Mn
2+
3
(Sb
5+
 
,Fe
3+
 
)(SiO
 
4
)(O,OH)
 
3
9.AF.75Welinite
Mn
2+
6
(W
6+
 
,Mg)
 
2
(SiO
 
4
)
 
2
(O,OH)
 
6
9.AF.80Ellenbergerite
Mg
 
6
(Mg,Ti,Zr,◻)
 
2
(Al,Mg)
 
6
Si
 
8
O
 
28
(OH)
 
10
9.AF.85Chloritoid
(Fe
2+
 
,Mg,Mn
2+
 
)Al
 
2
(SiO
 
4
)O(OH)
 
2
9.AF.85Magnesiochloritoid
MgAl
 
2
(SiO
 
4
)O(OH)
 
2
9.AF.85Ottrélite
(Mn
2+
 
,Fe
2+
 
,Mg)Al
 
2
(SiO
 
4
)O(OH)
 
2
9.AF.90Poldervaartite
CaCa[SiO
 
3
(OH)](OH)
9.AF.90Olmiite
CaMn
2+
 
[SiO
 
3
(OH)](OH)
Related Minerals - Hey's Index Grouping:

- +
15.1Andalusite
Al
 
2
(SiO
 
4
)O
15.2Kyanite
Al
 
2
(SiO
 
4
)O
15.4Mullite
Al
 
4+2x
Si
 
2-2x
O
 
10-x
15.5Pyrophyllite
Al
 
2
(Si
 
4
O
 
10
)(OH)
 
2
15.6Dickite
Al
 
2
(Si
 
2
O
 
5
)(OH)
 
4
15.7Nacrite
Al
 
2
(Si
 
2
O
 
5
)(OH)
 
4
15.8Kaolinite
Al
 
2
(Si
 
2
O
 
5
)(OH)
 
4
15.9Metahalloysite
15.10Halloysite
Al
 
2
(Si
 
2
O
 
5
)(OH)
 
4
15.11Allophane
(Al
 
2
O
 
3
)(SiO
 
2
)
 
1.3-2
· 2.5-3H
 
2
O

Other Names for Sillimanite

Synonyms:
BamblitBamliteBournonite (of Lucas)BucholziteFaserkiesel (of Lindacker)
FriboliteMonroeliteMonroliteSelmanite
Other Languages:
Croatian:Sillimanit
Dutch:Sillimaniet
Finnish:Andalusiitti
French:Sillimanite
German:Sillimanit
Buchholzit
Bucholzit
Fibrolit
Fibrolith
Glanzspat
Monrolit
Hebrew:סילימניט
Hungarian:Szillimanit
Italian:Sillimanite
Japanese:珪線石
Polish:Sillimanit
Russian:Силлиманит
Simplified Chinese:硅线石
Spanish:Sillimanita
Bucholzita
Fibrolita
Monrolita
Swedish:Sillimanit
Varieties:
Fibrolite

Other Information

Fluorescence in UV light:Not fluorescent.
Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Industrial Uses:Used as a source for synthesizing high-temperature industrial ceramics.

References for Sillimanite

Reference List:

- +
Bowen G.T. (1824), American Journal of Science, 8, 113.

Clark, S.P., E.C. Robertson & F. Birch (1957), Experimental determination of kyanite-sillimanite equilibrium relations at high temperatures and pressure: American Journal of Science: 255: 628-640.

Pearson, G.R. and Shaw, D.M. (1960) Trace elements in kyanite, sillimanite and andalusite. American Mineralogist: 45: 808-817.

Burnham, C.W. (1963a) Refinement of the crystal structure of sillimanite. Zeitschrift für Kristollographie: 118: 127-148.

Chinner, G.A., J.W. Smith & C.R. Knowles (1969), Transition metal contents of Al2SiO5 polymorphs: American Journal of Science: 267A: 96-113.

Raymond, M. and Hafner, S.S. (1970) Nuclear quadrupole coupling tensors of 27 Al in sillimanite Al2SiO5). Journal of Chemical Physics: 53: 4110-4111.

Finger, L.W. and Prince, E. (1972) Neutron diffraction studies: andalusite and sillimanite. Carnegie Institution of Washington, Year Book: 71: 496-500.

Vaughan, M.T. and Weidner, D.J. (1978) The relationship of elasticity and crystal structure in andalusite and sillimanite. Physics and Chemistry of Minerals: 3: 133-144.

Vernon, R.H. (1979) Formation of late sillimanite by hydrogen metasomatism (base-leaching) in some high-grade gneisses. Lithos: 12: 143-152.

Winter, J.K. and Ghose, S. (1979) Thermal expansion and high-temperature crystal chemistry of the Al2SiO5 polymorphs. American Mineralogist: 64: 573-586.

Grew, E.S. (1980a) Sillimanite and ilmenite from high grade metamorphic rocks of Antarctica and other areas. Journal of Petrology: 21: 39-68.

Fleet, M.E. and Arima, M. (1985) Oriented hematite inclusions in sillimanite. American Mineralogist: 70: 1232-1237.

Grew, E.S. and Rossman, G.R. (1985) Co-ordination of boron in sillimanite. Mineralogical Magazine: 49: 132-135.

Vernon, R.H., Flood, R.H., and D'Arcy, W.F. (1987) Sillimanite and andalusite produced by base-cation leaching and contact metamorphism of felsic igneous rocks. Journal of Metamorphic Geology: 5: 439-450.

Kerrick, D.M. (1990) Metamorphic reactions. In D.M. Kerrick, Ed., The Al2SiO5 polymorphs. 22, 223-253. Reviews in Mineralogy. Mineralogical Society of America, Chantilly, Virginia.

Kerrick, D.M. (1990) The Al2SiO5 polymorphs, 22, 406 p. Reviews in Mineralogy, Mineralogical Society of America, Chantilly, Virginia.

American Mineralogist (1992): 77: 374.

Yang, H., Hazen, R.M., Finger, L.W., Prewitt, C.T., and Downs, R.T. (1997b) Compressibility and crystal structure of sillimanite, Al2SiO5, at high pressure. Physics and Chemistry of Minerals: 25: 39-47.

Rao, M.N., Chaplot, S.L., Choudhury, N., Rao, K.R., Azuah, R.T., Montfrooji, W.T., and Bennington, S.M. (1999) Lattice dynamics and inelastic neutron scattering from sillimanite and kyanite Al2SiO5. Physical Review: B60: 12061.

Dahaoui, S., Ghermani, N.E., Ghose, S., and Howard, J.A.K. (2001) Electric field gradient tensors at the aluminum sites in the Al2SiO5 polymorphs from CCD high resolution X-ray diffraction data: comparison with 27 Al NMR results. American Mineralogist: 86: 159-164.

Iglesias, M., Schwarz, K., Blaha, P., and Baldomir, D. (2001) Electronic structure and electric field gradient calculations of Al2SiO5 polymorphs. Physics and Chemistry of Minerals: 28: 67-75.

Winkler, B., Hytha, M., Warren, M.C., Milman, V., Gale, J.D., and Schreuer, J. (2001) Calculation of the elastic constants of the Al2SiO5 olymorphs andalusite, sillimanite, and kyanite. Zeitschrift für Kristallographie: 216: 67-70.

Friedrich, A., Kunz, M., Winkler, B., and Le Bihan T. (2004) High-pressure beahvior of sillimanite and kyanite: compressibility, decomposition and indications of a new high-pressure phase. Zeitschrift für Kristallographie: 219: 324-329.

Burt, J.B., Ross, N.L., Angel, R.J., and Koch, M. (2006) Equations of state and structures of andalusite to 9.8 GPa and sillimanite to 8.5 GPa. American Mineralogist: 91: 319-326.

Ohuchi, F.S., Ghose, S., Engelhard, M.H., and Baer, D.R. (2006) Chemical bonding and electronic structures of the Al2SiO5 polymorphs, andalusite, sillimanite, and kyanite: X-ray photoelectron- and electron energy loss spectroscopy studies. American Mineralogist: 91: 740-746.

Best Localities for Sillimanite

Best of Species:Sillimanite

Internet Links for Sillimanite

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    Localities for Sillimanite

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