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Sillimanite

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Benjamin Silliman
Formula:
Al2(SiO4)O
System:
Orthorhombic
Colour:
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:

Classification of Sillimanite

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
9.AF.05

9 : SILICATES (Germanates)
A : Nesosilicates
F : Nesosilicates with additional anions; cations in [4], [5] and/or only [6] coordination
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
15.3

15 : Silicates of Aluminum
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Type Occurrence of Sillimanite

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:

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

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:
3.23 - 3.27 g/cm3 (Measured)    3.24 g/cm3 (Calculated)

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:
Data courtesy of RRUFF project at University of Arizona, used with permission.
X-Ray Powder Diffraction Data:
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
Max Birefringence:
δ = 0.016 - 0.023
Image 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:
Al2(SiO4)O
Essential elements:
All elements listed in formula:
Common Impurities:
Fe

Relationship of Sillimanite to other Species

Common Associates:
9.AF.10AndalusiteAl2(SiO4)O
9.AF.10KanonaiteMn3+Al(SiO4)O
9.AF.15KyaniteAl2(SiO4)O
9.AF.20MulliteAl4+2xSi2-2xO10-x
9.AF.20Krieselite(Al,Ga)2(GeO4)(OH)2
9.AF.23BoromulliteAl9BSi2O19
9.AF.25YoderiteMg(Al,Fe3+)3(SiO4)2O(OH)
9.AF.30MagnesiostauroliteMg(Mg,Li)3(Al,Mg)18Si8O44(OH)4
9.AF.30StauroliteFe22+Al9Si4O23(OH)
9.AF.30ZincostauroliteZn2Al9Si4O23(OH)
9.AF.35TopazAl2(SiO4)(F,OH)2
9.AF.40NorbergiteMg3(SiO4)(F,OH)2
9.AF.45AlleghanyiteMn52+(SiO4)2(OH)2
9.AF.45Chondrodite(Mg,Fe2+)5(SiO4)2(F,OH)2
9.AF.45ReinhardbraunsiteCa5(SiO4)2(OH,F)2
9.AF.45KumtyubeiteCa5(SiO4)2F2
9.AF.45HydroxylchondroditeMg5(SiO4)2(OH)2
9.AF.50Humite(Mg,Fe2+)7(SiO4)3(F,OH)2
9.AF.50Manganhumite(Mn2+,Mg)7(SiO4)3(OH)2
9.AF.50Unnamed (Ca-analogue of Humite)Ca7(SiO4)4F2
9.AF.55ClinohumiteMg9(SiO4)4F2
9.AF.55SonoliteMn92+(SiO4)4(OH,F)2
9.AF.55HydroxylclinohumiteMg9(SiO4)4(OH)2
9.AF.60LeucophoeniciteMn72+(SiO4)3(OH)2
9.AF.65Ribbeite(Mn2+,Mg)5(SiO4)2(OH)2
9.AF.70JerrygibbsiteMn92+(SiO4)4(OH)2
9.AF.75FranciscaniteMn62+(V5+,☐)2(SiO4)2(O,OH)6
9.AF.75ÖrebroiteMn32+(Sb5+,Fe3+)(SiO4)(O,OH)3
9.AF.75WeliniteMn62+(W6+,Mg)2(SiO4)2(O,OH)6
9.AF.80EllenbergeriteMg6(Mg,Ti,Zr,◻)2(Al,Mg)6Si8O28(OH)10
9.AF.85Chloritoid(Fe2+,Mg,Mn2+)Al2(SiO4)O(OH)2
9.AF.85MagnesiochloritoidMgAl2(SiO4)O(OH)2
9.AF.85Ottrélite(Mn2+,Fe2+,Mg)Al2(SiO4)O(OH)2
9.AF.90PoldervaartiteCaCa[SiO3(OH)](OH)
9.AF.90OlmiiteCaMn2+[SiO3(OH)](OH)
15.1AndalusiteAl2(SiO4)O
15.2KyaniteAl2(SiO4)O
15.4MulliteAl4+2xSi2-2xO10-x
15.5PyrophylliteAl2(Si4O10)(OH)2
15.6DickiteAl2(Si2O5)(OH)4
15.7NacriteAl2(Si2O5)(OH)4
15.8KaoliniteAl2(Si2O5)(OH)4
15.9Metahalloysite
15.10HalloysiteAl2(Si2O5)(OH)4
15.11Allophane(Al2O3)(SiO2)1.3-2 · 2.5-3H2O

Other Names for Sillimanite

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.
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.

Internet Links for Sillimanite

Specimens:
The following Sillimanite specimens are currently listed for sale on minfind.com.

Localities for Sillimanite

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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