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INVESTIGATIONS

Stone

RI min

RI max

Biref min

Biref max

Dens min

Dens max

Colour

Location

Info

ne min

ne max

no min

no max

Spectrum

UVS

UVL

Reference

Zircon - low

1.782

1.782

 

 

3.922

3.922

very dark green

Sri Lanka

metamict

 

 

 

 

 

 

 

The Journal of Gemmology 1974 N°4, p168-169

Zircon

 

 

 

 

4

4

yellowish green

Ilakaka, Fianarantsoa, Madagascar

2.01ct

 

 

 

 

broad absorption below 430nm and above 650nm

inert

inert

GIA Gem Database  35605

Zircon

1.83

1.838

0.006

0.008

4.04

4.06

brown, green, yellow, reddish brown, yellowish brown

Elahera, Sri Lanka

 

 

 

 

 

653, many lines

weak to distinct greenish yellow

weak to distinct yellowish

Gems & Gemology 1986 Summer, p91

Zircon

1.83

1.83

 

 

4.04

4.04

light brown

Bibilé, Sri Lanka

cat's-eye

 

 

 

 

660, 653, 621, 589 nm

 

 

The Journal of Gemmology 1988 Vol 21, N°2, p88-91

Zircon

 

 

 

 

4.07

4.04

yellowish green

Sabaragamuwa Province, Sri Lanka

7.11ct

 

 

 

 

broad absorption below 430nm  and above 660nm; line at 520nm

inert

inert

GIA Gem Database  33717

Zircon

 

 

 

 

4.12

4.12

yellowish green

Sabaragamuwa Province, Sri Lanka

6.21ct

 

 

 

 

broad absorption below 430nm ; lines at 485, 518, 539, 589, 653nm

inert

inert

GIA Gem Database  33734

Zircon

 

 

 

 

4.15

4.15

brown with PLAY of COLOUR (green and red)

 

 

 

 

 

 

 

weak slightly chalky

inert

Gems & Gemology 1997 summer, p141

Zircon

1.922

1.983

0.06

0.06

4.334

4.654

colourless

Champassak district, Thailand

heat treated

1.982

1.983

1.922

1.923

653nm line or doublet

inert or orange

orange

The Journal of Gemmology 1993 Vol23, N°7, p387-392

Zircon

 

 

 

 

4.53

4.53

yellowish-brown

Sri Lanka

24.92 ct, aventurescence caused by reflection of light at very thin and partly circular cracks

 

 

 

 

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1996 Dec, p153

Zircon

 

 

 

 

4.54

4.54

greenish brown

Sri Lanka

 

 

 

 

 

absorption lines in the red

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1998 Sep, p169

Zircon

 

 

 

 

4.55

4.55

dark orange

Tunduru, Ruvuma Region, Tanzania

8.74ct

 

 

 

 

broad absorption below 420nm  and above 670nm

weak orangy yellow

inert

GIA Gem Database  33756

Zircon

1.922

1.982

0.06

0.06

4.555

4.555

golden

Kha district, Vietnam

heat treated

 

 

 

 

653nm line, general absorption of blue and violet

mustard

inert

The Journal of Gemmology 1993 Vol23, N°7, p387-392

Zircon

 

 

 

 

4.57

4.69

brownish red

Muling, China

high zircon

 

 

 

 

some faint lines below 600nm

 

 

Gems & Gemology 2011 Spring, p36-41

Zircon

 

 

 

 

4.57

4.69

brownish red

Muling, China

high zircon

 

 

 

 

some faint lines below 600nm

 

 

Gems & Gemology 2011 Spring, p36-41

Zircon

1.922

1.984

0.056

0.061

4.593

4.657

colourless

Kha district, Vietnam

heat treated

1.979

1.984

1.922

1.923

653nm line

inert

mustard

The Journal of Gemmology 1993 Vol23, N°7, p387-392

Zircon

1.92

1.97

 

 

4.6

4.69

whitish-grey

Sri Lanka

heat-treated cat's-eye

 

 

 

 

660, 691, 662, 653, 621, 615, 589, 562, 538, 516nm

 

 

The Journal of Gemmology 1988 Vol 21, N°2, p88-91

Zircon

 

 

 

 

4.62

4.72

pink, purple, yellow-brown, orangy brown, near colourless (heat treated)

 

 

 

 

 

 

prominent 653nm, weak bands 535, 590,657, 689

moderate to very strong: yellow, brownish yellow, yellowish orange

weak to strong: yellowish, brownish yellow, yellowish orange

Gems & Gemology 1989 winter p207-215

Zircon

 

 

 

 

4.64

4.64

orangy yellow

Mount Meru, Arusha, Tanzania

12.81ct

 

 

 

 

broad absorption below 420nm  ; lines at 437, 485, 518, 539, 562, 589, 653, 690nm

inert

inert

GIA Gem Database  34341

Zircon

1.921

1.982

0.061

0.061

4.649

4.649

pale brown

Pailin district, Cambodia

 

 

 

 

 

no visible spectrum

orange

orange

The Journal of Gemmology 1993 Vol23, N°7, p387-392

Zircon

 

 

 

 

4.65

4.69

brown to brownish red

Cambodia

 

 

 

 

 

653nm line

inert

inert

The Australian Gemmologist 2011 Apr-Jun, p150

Zircon

1.923

1.983

0.06

0.06

4.67

4.67

strong gold

Kha district, Vietnam

 

 

 

 

 

 

inert

inert

The Journal of Gemmology 1993 Vol23, N°7, p387-392

Zircon

1.946

1.946

 

 

4.67

4.67

colourless

 

RI reading gemmeter; 1.1ct

 

 

 

 

 

 

 

ACAM Lab 

Zircon

1.957

1.962

 

 

4.67

4.72

brown, yellow-brown, yellow, red, brownish pink pink, pinkish brown

Bombo River, Umba valley, Tanzania

 

 

 

 

 

690, 682, 653, 620, 615, 589, 562, 538, 510nm

distinct to strong brown

weak to strong brown

The Australian Gemmologist 2009 Vol 23, N°10, p453-456

Zircon

1.922

1.982

0.06

0.06

4.679

4.679

red

Champassak district, Thailand

 

 

 

 

 

 

inert

inert

The Journal of Gemmology 1993 Vol23, N°7, p387-392

Zircon

 

 

 

 

4.68

4.68

greenish yellow

Ilakaka, Fianarantsoa, Madagascar

7.66ct

 

 

 

 

broad absorption below 420nm ; lines at 477, 485, 513, 518, 539, 543, 562, 589, 615, 621, 653, 660, 690nm

inert

inert

GIA Gem Database  35601

Zircon

 

 

 

 

4.68

4.68

greenish blue

Thailand

28.15ct

 

 

 

 

broad absorption below 420nm ; lines at 543, 596, 660nm

inert

inert

GIA Gem Database  33695

Zircon

1.923

1.985

0.062

0.062

4.68

4.68

colour changing : blue in daylight to green in incandescent light

 

2.25ct

 

 

 

 

strong uranium spectrum

inert

inert

Gems & Gemology 1995 Fall, p212-213

Zircon

1.922

1.982

0.06

0.06

4.695

4.695

orangy-white

Champassak district, Thailand

heat treated

 

 

 

 

653nm line

inert

orange

The Journal of Gemmology 1993 Vol23, N°7, p387-392

Zircon

 

 

 

 

4.7

4.7

reddish brown

Yabelo, Ethiopia

13.01ct

 

 

 

 

 

weak orange with yellow chalkiness

 

Gems & Gemology 2011 Fall, p247

Zircon

 

 

 

 

4.7

4.7

dark orange

Dodoma Region, Tanzania

21.05ct

 

 

 

 

broad absorption below 430nm

inert

inert

GIA Gem Database  35070

Zircon

 

 

 

 

4.7

4.7

light yellowish orange

Thailand

11.48ct

 

 

 

 

broad absorption below above 670nm; lines at 485, 518, 539, 562, 589, 615, 653, 657nm

weak greenish blue

weak orangy yellow

GIA Gem Database  33719

Zircon

 

 

 

 

4.7

4.7

yellowish orange

Thailand

15.13ct

 

 

 

 

broad absorption below 440nm  and above 660nm

inert

inert

GIA Gem Database  35092

Zircon

 

 

 

 

4.7

4.7

greenish blue

Thailand

19.31ct

 

 

 

 

broad absorption below 430nm and above 660nm; lines at 518, 539, 562, 589, 653nm

inert

inert

GIA Gem Database  33746

Zircon

 

 

 

 

4.71

4.71

colourless

Sri Lanka

4.54ct

 

 

 

 

many absorption lines

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1999 Jul p106

Zircon

 

 

 

 

4.71

4.72

colourless

Solomon Islands

0.79 - 2.50 ct

 

 

 

 

two lines in the red region, stronger at 653.5 nm

moderate white

moderate yellowish orange

Gems & Gemology 2010 spring, p67

Zircon

1.923

1.969

0.046

0.046

4.719

4.719

mid blue

Kha district, Vietnam

heat treated

 

 

 

 

653nm line

inert

inert

The Journal of Gemmology 1993 Vol23, N°7, p387-392

Zircon

 

 

 

 

4.72

4.72

orange

Australia

1.80ct, tenebrescent

 

 

 

 

 

 

 

Gems & Gemology 2011 Winter, p314-315

Zircon

 

 

 

 

4.75

4.75

orange

Thailand

4.06ct

 

 

 

 

broad absorption below 440nm  and above 660nm

inert

inert

GIA Gem Database  35091

Zircon

1.87

1.87

 

 

4.75

4.75

greenish-blue (strong sky blue)

Cambodia

heated, 6.19ct, RI mesured by reflectivity, doubled facets edges can be easily observed

 

 

 

 

 

inert

inert

http://www.spec4gem.info/index.php 2015

Zircon

 

 

 

 

4.79

4.79

reddish orange

Cambodia

6.61ct

 

 

 

 

broad absorption below 430nm and above 670nm

inert

inert

GIA Gem Database  33723

Zircon

 

 

 

 

 

 

brownish reddish orange

Myanmar

21.87ct

 

 

 

 

numerous lines: 432, 484, 521, 537, 562, 589, 660, 662 and 691 nm

weak orange

weak orange

The Journal of Gemmology 2015 Vol 34, No.5, p397

 

TABLES

Stone

RI min

RI max

Biref min

Biref max

Dens min

Dens max

ne min

ne max

no min

no max

Reference

Zircon

1.777

2.01

0

0.059

3.9

4.8

 

 

 

 

http://www.gemmology.be 

Zircon - low

1.777

1.85

 

 

3.9

4.1

 

 

 

 

http://www.geminterest.com 

Zircon - low

1.777

1.781

 

0.004

3.9

4.1

 

 

 

 

Tables of Gemstone Identification, Roger Dedeyne, Ivo Quintens, 2007 

Zircon - low

1.78

1.85

 

0.008

3.9

4.1

1.780

1.850

1.780

1.850

Joel Arem, Color Encyclopedia of Gemstones, 1987 

Zircon - low

1.78

1.78

0.005

0.005

3.95

4.1

 

 

 

 

Tabellen zur Edelstein-Bestimmung, Pschichholz FGA, 1975 

Zircon - low

1.78

1.81

 

 

3.95

4.1

 

 

 

 

John Sinkakas, Gemstone and mineral data book,1972 

Zircon - low

1.78

1.81

 

 

3.9

4.1

 

 

 

 

Gems, R Webster, 5th edition 1994 

Zircon - low

1.78

1.84

0.002

0.005

3.93

4.07

 

 

 

 

Bestimmungstabellen für Edelsteine, Birgit Günther, 2008 

Zircon

1.78

2.024

0

0.059

3.9

4.73

 

 

 

 

Gemology Tools Professional 2010

Zircon - low

1.78

1.85

0

0.008

3.9

4.1

 

 

 

 

Gemology Tools Professional 2010

Zircon - low

1.78

1.85

0.001

0.003

3.87

4.1

 

 

 

 

Gemmo.eu 2013

Zircon - low

1.785

1.848

0.001

0.008

3.9

4

1.780

1.848

1.785

1.850

Gemme, Dati per l'identificazione, P. De Stefano et al, 1993 

Zircon

1.79

2.015

0.005

0.055

3.91

4.73

1.795

2.015

1.790

1.960

Gemmological Tables, Ulrich Henn, 2004 

Zircon - medium

1.84

1.97

0.008

0.043

4.1

4.65

1.850

1.970

1.840

1.930

Joel Arem, Color Encyclopedia of Gemstones, 1987 

Zircon - medium

1.846

1.97

0.006

0.043

4.08

4.65

1.850

1.970

1.846

1.930

Tables of Gemstone Identification, Roger Dedeyne, Ivo Quintens, 2007 

Zircon - medium

1.85

1.945

0.006

0.05

4.07

4.65

1.865

1.945

1.850

1.920

Gemme, Dati per l'identificazione, P. De Stefano et al, 1993 

Zircon - high

1.864

2.015

0.036

0.059

4.64

4.7

1.970

2.015

1.864

1.970

http://www.geminterest.com 

Zircon - medium

1.875

1.935

0.006

0.05

4.07

4.57

 

 

 

 

Bestimmungstabellen für Edelsteine, Birgit Günther, 1981 

Zircon - high

1.92

2.01

0.036

0.059

4.65

4.8

1.970

2.010

1.920

1.940

Joel Arem, Color Encyclopedia of Gemstones, 1987 

Zircon - high

1.923

2.024

0.36

0.059

4.65

4.8

1.944

2.024

1.920

1.940

Gemme, Dati per l'identificazione, P. De Stefano et al, 1993 

Zircon - high

1.923

2.01

0.04

0.06

4.5

4.75

 

 

 

 

Gemmo.eu 2013

Zircon - high

1.925

2.024

0.059

0.059

4.67

4.73

 

 

 

 

Bestimmungstabellen für Edelsteine, Birgit Günther, 1981 

Zircon - high

1.925

1.984

0.059

0.059

4.67

4.7

 

 

 

 

Gems, R Webster, 5th edition 1994 

Zircon - high

1.925

2.01

0.036

0.059

4.65

4.8

1.970

2.010

1.925

1.940

Tables of Gemstone Identification, Roger Dedeyne, Ivo Quintens, 2007 

Zircon - high

1.926

1.985

0.059

0.059

4.67

4.71

 

 

 

 

Tabellen zur Edelstein-Bestimmung, Pschichholz FGA, 1975 

Zircon - medium

 

 

 

 

4.1

4.6

 

 

 

 

John Sinkakas, Gemstone and mineral data book,1972 

Zircon - high

 

 

0.059

0.059

4.67

4.7

 

 

 

 

John Sinkakas, Gemstone and mineral data book,1972 

 

CAUSE OF COLOUR

Stone

Colour

Cause of colour

Reference

Zircon

blue

U4+

Gems & Gemology Summer 1988

Zircon

brown

presence of small amounts of uranium and thorium

Gems & Gemology Summer 1981 p65

Zircon

brown, amber

radioactive decay and the resulting radiation damage centers

http://minerals.caltech.edu

Zircon

green

associated with a mixture of the blue color from uranium and red-brown color from radiation damage centers

http://minerals.caltech.edu

Zircon

red

Nb4+ colour centers

Gems & Gemology Summer 1988

 

MINERAL INCLUSIONS

Inclusion

Stone

Reference

actinolite

Zircon

E.J. Gübelin and J.I. Koivula, Photoatlas of inclusions in Gemstones, volume 2 (2005)

apatite

Zircon

E.J. Gübelin and J.I. Koivula, Photoatlas of inclusions in Gemstones, volume 2 (2005)

biotite

Zircon

E.J. Gübelin and J.I. Koivula, Photoatlas of inclusions in Gemstones, volume 2 (2005)

goethite

Zircon

The Journal of Gemmology, 1993, Vol23, N°7, p390

hematite

Zircon

E.J. Gübelin and J.I. Koivula, Photoatlas of inclusions in Gemstones, volume 2 (2005)

ilmenite

Zircon

Webster, Gems 5th edition, p181 (1994)

limonite

Zircon

E.J. Gübelin and J.I. Koivula, Photoatlas of inclusions in Gemstones, volume 2 (2005)

magnetite

Zircon

Gems & Gemology 2011, Spring, p39

pyrite

Zircon

E.J. Gübelin and J.I. Koivula, Photoatlas of inclusions in Gemstones, volume 2 (2005)

rutile

Zircon

E.J. Gübelin and J.I. Koivula, Photoatlas of inclusions in Gemstones, volume 2 (2005)

 

LOCALITIES

STONE

LOCALITIES

REFERENCE

Zircon

Antanifotsy pegmatite, Faratsiho Department

Vakinankaratra Region (Betafo - Antsirabé region)

Antananarivo Province

Madagascar

Gems & Gemology 2000 winter p325

Zircon

Departementa Betroka

Horombe region

Fianarantsoa Province

Madagascar

Gems & Gemology 2000 winter p325

Zircon

Ilakaka gem deposit, Ilakaka, Departementa Ranohira

Horombe region

Fianarantsoa Province

Madagascar

Extra Lapis No 17

Zircon

Amboasary Department

Anosy (Fort Dauphin) Region

Tuléar (Toliara ) Province

Madagascar

Gems & Gemology 2000 winter p325

Zircon

Jemaa

Kaduna

 

Nigeria

http://www.keysminerals.com/africa.html

Zircon

 

Haputale

Badulla

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Passara

Badulla

Central Province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Avissawella

Kegalla

Central Province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Hatton

Nuwara Elyia

Central Province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Elahera

Polonnaruwa

Central Province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Rakwana

Ratnapura

Sabaragamuwa Province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Pelmadulla

Ratnapura

Sabaragamuwa province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Balangoda

Ratnapura

Sabaragamuwa province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Alutgama

Kalutara

Southern Province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Morawaka

Matara

Southern Province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Akuressa

Matara

Southern Province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Embilipitiya

Monaragata

Southern Province

Sri Lanka

Gems & Gemology 2000 winter p325

Zircon

Umba Valley

Lelatema Mts

Arusha Region

Tanzania

Gemmologie, 1997, Mar,p31

Zircon

 

Same

Kilimanjaro Region

Tanzania

Gems & Gemology 2000 winter p325

Zircon

 

Mashewa

Korogwe area

Tanzania

The Australian Gemmologist 2009 Vol23, N°10 p453-456

Zircon

 

Tunduru-Songea area

Ruvuma Region

Tanzania

Gemmologie, 1997, Mar,p31

Zircon

 

 

Singida Region

Tanzania

The Australian Gemmologist 2009 Vol23, N°10 p456-456

Zircon

 

 

Tanga Province

Tanzania

The Australian Gemmologist 2009 Vol23, N°10 p453-456

Zircon

Bombo river area

Umba River (Umba Valley)

Tanga Region

Tanzania

The Australian Gemmologist 2009 Vol23, N°10 p456-456

Zircon

 

Muhuwesi River

Tunduru

Tanzania

Gems & Gemology 2000 winter p325

Zircon

 

Champassak district

 

Thailand

Webster, Gems 5th edition (1994), p182

Zircon

 

Kha District

 

Vietnam

Webster, Gems 5th edition (1994), p182

 

CHEMICAL DATA (%)

Stone

Colour

Locality

Reference

SiO2

Al2O3

MnO

MgO

FeO

CaO

Fe2O3

P2O5

PbO

ZrO2

HfO2

ThO2

UO2

Zircon

brownish red

Muling

China

Gems & Gemology 2011, Spring, p40

33.14

0.05

 

0.03

 

0.03

 

 

 

63.75

1.16

 

 

Zircon

red

 

Nigeria

The Journal of Gemmology 1990, Vol22, N°4,p201

33.2

0.02

 

 

 

0.3

0.12

 

 

65.3

1.23

 

 

Zircon

orange

 

Nigeria

The Journal of Gemmology 1990, Vol22, N°4,p201

32.4

0.08

 

 

 

0.01

0.83

 

 

65.6

0.91

 

 

Zircon

orange

 

Nigeria

The Journal of Gemmology 1990, Vol22, N°4,p201

31.8

0.09

 

 

 

0.01

0.37

 

 

65.3

0.85

 

 

Zircon

near colourless

 

Nigeria

The Journal of Gemmology 1990, Vol22, N°4,p201

32.1

0.01

 

 

 

0.01

0.08

 

 

66.5

0.64

 

 

Zircon

green

 

Sri Lanka

Zeitschrift der Deutschen Gemmologischen Gesellschaft, 1985, 34, Nr1/2, p71

33.95

 

 

 

0.09

 

 

 

 

64.42

1.7

0.14

0.47

Zircon

violet

 

Sri Lanka

Zeitschrift der Deutschen Gemmologischen Gesellschaft, 1985, 34, Nr1/2, p71

34.27

 

 

 

0.03

 

 

 

 

65.72

1.19

0.1

0.12

Zircon

yellow

 

Sri Lanka

Zeitschrift der Deutschen Gemmologischen Gesellschaft, 1985, 34, Nr1/2, p71

33.52

 

 

 

0.03

 

 

 

 

65.18

1.4

0.08

0.16

Zircon

pink

 

Sri Lanka

Zeitschrift der Deutschen Gemmologischen Gesellschaft, 1985, 34, Nr1/2, p71

33.84

 

 

 

0.04

 

 

 

 

65.7

1.27

0.07

0.14

Zircon

light brown, cat's-eye

 

Sri Lanka

The Journal of Gemmology 1988, Vol 21, N°2, p90

34.28

 

 

 

0.04

 

 

 

 

63.7

1.4

 

 

Zircon

whitish-grey, cat's eye, heat treated

 

Sri Lanka

The Journal of Gemmology 1988, Vol 21, N°2, p90

33.96

 

 

 

 

 

 

 

 

65.1

1.19

0.25

0.67

Zircon

yellow

Bombo River, Umba valley

Tanzania

The Australian Gemmologist 2009,Vol 23, N°10, p454

32.62

 

 

 

 

 

0.01

0.04

 

67.5

0.88

0.01

0.24

Zircon

light brown

Bombo River, Umba valley

Tanzania

The Australian Gemmologist 2009,Vol 23, N°10, p454

32.56

 

0.03

 

 

 

0.01

0.04

0.13

67.61

0.67

0.01

0.01

Zircon

dark brown

Bombo River, Umba valley

Tanzania

The Australian Gemmologist 2009,Vol 23, N°10, p454

32.7

 

 

 

 

0.02

0.02

0.04

0.01

67.22

0.85

0.01

0.01