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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 (%)