Home            Gemstones

     

INVESTIGATIONS

Stone	RI min	RI max	Biref min	Biref max	Dens min	Dens max	Colour	Locality	Info	nx min	nx max	ny min	ny max	nz min	nz max	Spectrum	UVS	UVL	Reference
Sillimanite	1.577	1.587	0.017	0.018	3.26	3.26	yellow-green, greenish yellow	India	49.29, 25.05, and 21.12 ct	1.58	1.58			1.58	1.59	strong absorption band at 460 nm	inert	inert	Gems & Gemology 2006 Spring, p66-67
Sillimanite	1.654	1.673	0.019	0.019	3.28	3.28	bluish violet	Mogok, Myanmar	11.79ct								inert	inert	GIA Gem Database  34535
Sillimanite	1.655	1.675	0.02	0.02	3.26	3.26	colourless	Sri Lanka	0.94ct	1.655	1.655	1.659	1.659	1.675	1.675	none	weak pinkish violet	weak violet	ACAM Lab  2294
Sillimanite	1.656	1.675	0.019	0.019	3.25	3.25	light violet	Eheliyagoda, Sabaragamuwa Province, Sri Lanka	2.62ct								inert	inert	GIA Gem Database  34018
Sillimanite	1.658	1.677	0.019	0.019	3.25	3.25	light blue, colourless to greyish	sri Lanka											The Australian Gemmologist 1987 may, p241
Sillimanite	1.658	1.681	0.02	0.021	3.26	3.26	yellowish green to greenish yellow	Orissa, India	between 2.85 and 1063 cts	1.66	1.660			1.679	1.681				Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2006 Jun p59-61
Sillimanite	1.658	1.678	0.02	0.02	3.23	3.23	colourless	Sri Lanka	1.48ct										Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1999 Jul p106
Sillimanite	1.658	1.678	0.02	0.02	3.31	3.31	yellowish orange	Mogok, Myanmar	3.47ct								inert	inert	GIA Gem Database  34014
Sillimanite	1.658	1.678	0.02	0.02	3.38	3.38	light violet purplish	Mogok, Myanmar	11.16ct								inert	inert	GIA Gem Database  34552
Sillimanite	1.659	1.679	0.02	0.02	3.24	3.24	dyed red		7 to 12 ct	1.66	1.659	1.665	1.665	1.679	1.679				Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2005 Sep, p71-72
Sillimanite	1.659	1.679	0.02	0.02	3.22	3.22	red (dyed)		9.61 and 11.40ct, ruby imitation, biaxal +, dyed + impregnated, chelsea filter: pink							600 nm cut-off	inert	moderate red to long-wave with yellow emission along the fractures	Gems & Gemology 2005 Fall, p297
Sillimanite	1.659	1.679	0.02	0.02	3.22	3.22	dyed red (to imitate ruby)										inert with yellow emission along the fractures	moderate red with yellow emission along the fractures,	Gems & Gemology 2005 Fall, p274
Sillimanite	1.66	1.682	0.022	0.022	3.25	3.25		Elahera, Sri Lanka		1.66	1.660	1.662	1.662	1.682	1.682	4.62, 441, 410nm	inert	inert	Gems & Gemology 1986 Summer, p91
Sillimanite	1.66	1.682	0.022	0.022	3.3	3.3	light yellowish		biaxial positive								weak orange	weak orange	The Journal of Gemmology 1986 Vol20, N°3, p151
Sillimanite	1.66	1.66			3.196	3.226	greyish green with cat's eye		cat's eyes, 2 - 11.42 ct, almost opaque										The Journal of Gemmology 1982 Vol18, N°4 p277-281
Sillimanite	1.66	1.68	0.02	0.02	3.2	3.2	very dark brown		3.44ct, cabochon, cat's-eye, spot RI							general absorption up to about 490 nm, with a broad dark band superimposed at 440 to 450 nm	inert	inert	Gems & Gemology 1987 Fall, p167-168
Sillimanite	1.661	1.68	0.019	0.019	3.26	3.26	light grey		6.65 ct, resembling moonstone								inert	inert	Gems & Gemology 2006 Summer, p179
Sillimanite					3.25	3.25	green, brown, grey-violet	Guinea	cat's eyes, transparent to translucent, 1.99 to 4.79 ct										Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2009 58/3-4/Dec, p81
Sillimanite							green (dyed)		to imitate emerald, 14.5-43.5ct										Gems & Gemology 2009 Winter, p308-309

 

TABLES

Stone	RI min	RI max	Biref min	Biref max	Dens min	Dens max	nx min	nx max	ny min	ny max	nz min	nz max	Reference
Sillimanite	1.652	1.685	0.016	0.023	3.2	3.3							Gemmo.eu
Sillimanite	1.653	1.684	0.015	0.021	3.23	3.27							Gemology Tools Professional 2010
Sillimanite	1.654	1.674	0.013	0.021	3.22	3.27	1.654	1.661			1.684	1.674	Gemme, Dati per l'identificazione, P. De Stefano et al, 1993
Sillimanite	1.654	1.683	0.02	0.02	3.14	3.27							http://www.gemmology.be
Sillimanite	1.654	1.683	0.02	0.02	3.23	3.27	1.654	1.661	1.658	1.662	1.673	1.683	Joel Arem, Color Encyclopedia of Gemstones, 1987
Sillimanite	1.654	1.684	0.015	0.021	3.23	3.28	1.654	1.661	1.658	1.662	1.673	1.684	http://www.geminterest.com
Sillimanite	1.654	1.684	0.014	0.021	3.22	3.27	1.654	1.661	1.658	1.662	1.673	1.684	Tables of Gemstone Identification, Roger Dedeyne, Ivo Quintens, 2007
Sillimanite	1.655	1.684	0.014	0.021	3.22	3.26	1.655	1.661			1.677	1.684	Bestimmungstabellen für Edelsteine, Birgit Günther, 1981
Sillimanite	1.655	1.684	0.014	0.021	3.2	3.25	1.655	1.661	1.658	1.670	1.677	1.684	Gemmological Tables, Ulrich Henn, 2004
Sillimanite	1.657	1.679	0.015	0.021	3.22	3.26	1.657	1.659			1.673	1.679	Tabellen zur Edelstein-Bestimmung, Pschichholz FGA, 1975

 

CAUSE OF COLOUR

Stone	Colour	Cause of colour	Reference
Sillimanite	blue	Fe²+-O-Ti4+ charge transfer, simular to blue kyanite	Gems & Gemology Summer 1988
Sillimanite	yellow	Fe³+ or Cr³+ in tetrahedral coordination	Gems & Gemology Summer 1988
Sillimanite	brown	Fe features of yellow sillimanite plus inclusions of iron-rich phase	Gems & Gemology Summer 1988

 

MINERAL INCLUSIONS

Inclusion	Stone	Reference
apatite	Sillimanite	Gems & Gemology Summer 1986, p91
hematite	Sillimanite	The Journal of Gemmology 1982, Vol18, N°4 p277-281
magnetite	Sillimanite	The Journal of Gemmology 1982, Vol18, N°4 p277-281
rutile	Sillimanite	Gems & Gemology 2005 fall, p274
zircon	Sillimanite	Gems & Gemology Summer 1986, p91

 

LOCALITIES

STONE	LOCALITIES				REFERENCE
Sillimanite		Orissa		India	Gemmologie jun 2006 p60
Sillimanite		Vishakhapatnam	Andhra Pradesh	India	Gems & Gemology 2006 spring p 67-68
Sillimanite	Morawaka	Deniyaya district		Sri Lanka	Gems & Gemology 1988 Spring p58

 

CHEMICAL DATA (%)