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INVESTIGATIONS

Stone

RI min

RI max

Dens min

Dens max

Colour

Location

Info

Spectrum

UVS

UVL

Reference

Opal

1.36

1.44

1.74

1.89

play of colour with typically white bodycolour, some brown, fire and colourless

Wegel Tena, Wollo Province, Ethiopia

opaque to translucent, become transparent when soaked in water, "digit patterns"; chelsea: orange to bright red; black opaque xx (pyrite?)

 

inert to strong (weaker than UVL): bluish white, yellow, green

inert to strong: bluish white, yellow, green

Gems & Gemology 2010 Summer, p90-105

Opal

1.36

1.43

2

2

white, fire (red, orange, yellow), water-opal

Mexico

hardness litlle less than 6, somewhat lower than that of Australian opals, due to the greater water-content

 

 

 

The Australian Gemmologist 1986

Opal

1.37

1.41

1.7

1.77

purple (dyed)

probably : Wollo, Ethiopia

dyed hydrophane

 

 

 

Gems & Gemology 2011 Winter, p260-270

Opal

1.4

1.45

1.35

2.03

near colourless, milky white, yellow, orange, brown (good play of colours to weak)

Yita Ridge, Shewa (Showa) Province, Ethiopia

transparent to opaque; some brown stones appeared red

 

inert, faint to strong yellow-green, faint blue-white, blue, orange

inert, faint to weak yellow-green, blue, yellow, orange

Gems & Gemology 1996 summer, p112-120

Opal

1.4

1.44

1.99

2.01

colourless, yellow, brownish orange

Laverton, Western Australia

0.49-4.39ct, common opal

 

colourless: strong white

 

Gems & Gemology 2011 Winter, p318-319

Fire opal

1.415

1.46

2.05

2.26

yellow, orange, red (no play of colour)

Bemia, Madagascar

 

 

 

inert to moderate yellow-green

Gems & Gemology 2010 Summer, p114-121

Opal

1.42

1.445

1.92

2.08

green, yellow

Mali

 

 

 

 

Extra Lapis Nr 10 Opal 1996 p22

Opal

1.42

1.43

1.95

2.05

reddish orange  with colour play (predominantly green and red)

Queretaro, Mexico

often high degree of transparency

 

 

 

Gems & Gemology 1983 summer, p87-96

Opal

1.42

1.43

2.11

2.12

 

Andamooka, Australia

treated matrix

 

 

 

The Australian Gemmologist 2003 Vol 21,N°11, p446

Opal

1.42

1.43

 

 

intense hues of red, blue and green

Queensland, Australia

"boulder opal" : gem quality opal that retains some portion of the ironstone matrix when cut

 

 

 

Gems & Gemology 1993 spring, p4-15

Opal

1.42

1.47

1.3

2.2

hyalite, rainbow opal, fire opal, play-of-color varieties : contra luz, hydrophone, crystal opal

Opal Butte, Oregon, USA

hydrophane: density 1.3

 

 

 

Gems & Gemology 1988 Winter, p229-236

Opal

1.422

1.44

1.98

2.02

 

Tintenbar, Australia

 

 

 

 

The Australian Gemmologist 2003 Vol 21,N°11, p446

Opal

1.43

1.45

1.96

2.04

white, brown, dark brown, black

Java, Indonesia

 

 

inert to very faint chalky blue

inert to faint chalky blue

The Australian Gemmologist 2009 23, 513-528

Opal

1.43

1.452

2.01

2.08

blue

Acari, Nazca, Peru

hardness 5

 

inert

inert

The Journal of Gemmology 2001 Vol 27, N°6, p328-329

Opal

1.43

1.51

2.04

2.43

blue, pink, green

Acari, Nazca, Peru

translucent -> opaque

 

strong greenish yellow areas

 

The Australian Gemmologist 2007 Vol 23, N°1, p3-15

Opal

1.43

1.43

2.03

2.03

light to dark yellowish green with dendritic black inclusions

Brazil

translucent cabochons, 0.99, 2.22, and 1.84 ct, spot RI

 

inert

inert

Gems & Gemology 1986 p110

Fire opal

1.431

1.431

2.05

2.05

orange

Opal Butte, Oregon, USA

 

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1997 Sep, p161-168

Opal

1.435

1.468

1.98

2.06

colourless (water-opal), brown (tea-opal), grey, black

Java (Rangkasbitung, Banten Province)

 

 

inert

inert

The Journal of Gemmology 2007 Nr 7/8, p383-397

Opal

1.435

1.468

1.98

2.06

with play-of-colour: white (milky to white), black (blackish brown); fire opal: yellowish reddish;  colourless; without play: colourless, greenish, yellowish, brown

Java, Indonesia

 

 

 

 

The Australian Gemmologist 2005 Vol 22, N°6, p254-259

Opal

1.435

1.468

1.98

2.06

 

Java, Indonesia

 

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2004

Opal

1.438

1.442

2.03

2.06

green

Turkey

Cr³+ chromophore

two broad bands at 599 and 370nm, sharp line at 681nm

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1997 Mar, p2

Fire opal

1.439

1.447

1.98

2

orange-red, play of colour

Ethiopia

 

cut-off at 600nm

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1997 Mar, p4

Fire opal

1.439

1.441

1.99

2.03

orange-red to fire-red

Campos Borges, Rio Grande do Sul, Brazil

2.95, 3.64, 7.33 ct

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1995 Sep, p43-46

Opal

1.44

1.45

1.98

2.05

black matrix (after treatment)

Andamooka, Australia

hardness 6

 

 

blue-white

Gems & Gemology 1991 Summer, p100-106

Opal

1.44

1.453

2.09

2.13

black

Lightning Ridge, Australia

 

 

 

 

The Australian Gemmologist 2003 Vol 21,N°11, p446

Opal

1.44

1.46

2.11

2.13

light

Andamooka, Australia

 

 

 

 

The Australian Gemmologist 2003 Vol 21,N°11, p446

Opal

1.44

1.44

2.14

2.14

greenish blue to blue, turquoise

Andes Mts, Peru

translucent

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1995 Mar, p5

Opal

1.44

1.44

2.18

2.18

purple

Mexico

common opal, coloured by fluorite inclusions, trade name: opal royale

 

very strong green

weak green

Gems & Gemology 2012 Spring, p56

Opal

1.44

1.48

2.14

2.14

yellow

West Africa

transparent to translucent

 

inert

inert

Gems & Gemology 2012 Fall, p226-227

Fire opal

1.44

1.44

2.02

2.02

yellow

Tuléar Province, Madagascar

1.72ct

 

inert

inert

ACAM Lab  1833

Opal

1.44

1.44

2.03

2.11

yellow, orange, brownish orange, and orangy brown

Tanzania

4.04 - 6.71 ct, cabochon, cats-eye, spot RI

 

inert

inert

Gems & Gemology 1998 Summer, p137-138

Opal

1.44

1.44

2.02

2.02

black (dark orange-brown in intense transmitted light), play of colour in the form of chatoyant bands

Jalisco, Mexico

cabochon 2.16ct, spot RI

 

 

 

Gems & Gemology 1990 Winter, p304

Opal

1.44

1.445

2.02

2.04

yellow-green to orange

Argentina

4.26 - 8.06 ct, cabochons, opaque to transparent

 

inert

inert to very weak whitish green

Gems & Gemology 2009 Fall, p220

Fire opal

1.442

1.446

2

2.02

 

Shaphané Mts, Turkey

0.73 ct , 1.27 ct

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1995 Mar, p5

Opal

1.442

1.455

2.05

2.11

light

Coober Pedy, Australia

 

 

 

 

The Australian Gemmologist 2003 Vol 21,N°11, p446

Opal

1.445

1.445

2.11

2.11

greenish-yellow

Sri Lanka

cat's eye, 7.58ct

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1999 Mar, p3

Opal

1.445

1.458

2.12

2.13

 

Lambina, Australia

 

 

 

 

The Australian Gemmologist 2003 Vol 21,N°11, p446

Opal

1.446

1.448

2.13

2.15

turquoise blue

Brazil

translucent to transparent, 1.53 to 4.90 ct

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1996 Dec, p155

Opal

1.446

1.453

2.05

2.15

greenish yellow

Nioro du Sahel, Kayes, Mali

2.74ct

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2013 62/1-2, Jun, p46-48

Fire opal

1.448

1.448

2.06

2.06

orange, yellow

Aleksejewskoje, Kazakhstan

 

 

 

 

Zeitschrift der Deutschen Gemmologischen Gesellschaft 1991 Apr, p11-23

Opal

1.45

1.47

2

2.06

blue-green, translucent

110 km NW of Shahr-e Babak, Kerman Province, Iran

 

600nm cut-off

inert

inert

Gems & Gemology 2007 fall p 257

Opal

1.45

1.46

2.08

2.1

light

White Cliffs, Australia

 

 

 

 

The Australian Gemmologist 2003 Vol 21,N°11, p446

Opal

1.45

1.457

2.09

2.1

potch

Lightning Ridge, Australia

 

 

 

 

The Australian Gemmologist 2003 Vol 21,N°11, p446

Opal

1.45

1.45

2.11

2.11

blue

Lily Mine, Peru

 

cutoff at around 650nm

very weak bluish

very weak bluish

Gems & Gemology 2003 winter p 332

Opal

1.45

1.456

2.11

2.13

 

Mintabie, Australia

 

 

 

 

The Australian Gemmologist 2003 Vol 21,N°11, p446

Opal

1.45

1.49

2.16

2.22

pink

Peru

mixture of palygorskite, opal and chalcedony, hardness 6

 

colourless veinlets : bright green

pinkish-white

The Journal of Gemmology 2001 Vol 27, N°6, p328-329

Opal

1.45

1.54

2.23

2.44

blue, light greyish blue with play of colour

Southern Skies Mine, Arizona

patterns of blue opal in a mostly brown matrix, spot RI

 

weak blue, yellow

 

Gems & Gemology 2012 Fall, p226

Opal

1.45

1.45

2.14

2.14

white

Milford, Utah, USA

37.18ct, cabochon, botryoidal

 

inert

inert

Gems & Gemology 1997 Spring, p63-64

Opal

1.45

1.45

2.08

2.08

brownish yellow

 

9.00 ct, cabochon, cat's-eye

 

weak red

inert

Gems & Gemology 1998 Spring, p44-45

Opal

1.45

1.45

2.08

2.08

brownish yellow

 

0.76ct cabochon, cat's-eye, exhibits a strong "milk-and-honey" effect

 

weak red

weak red

Gems & Gemology 1990 Fall,p230

Opal

1.45

1.45

2.16

2.23

pink

 

spot RI

weak band at 490 nm, a weak line at 550 nm, and a cutoff from 430 nm

very
weak yellow to inert

weak-to-medium whitish

Gems & Gemology 2004 Fall, p246

Opal

1.45

1.47

2.01

2.01

greenish yellow

Brazil

2.76ct, cat's-eye

general absorption up to 530 nm and weak bands at 620 nm and 670 nm

inert

dull yellow-green

Gems & Gemology 1992 Fall, p194

Opal

1.45

1.45

2.12

2.16

light to very light yellow, green (caused by day-light fluorescence)

Mexico

0.83 - 1.81 ct, RI  approximately 1.45, transparent (hyalite), "electric opal"

 

 

 

The Journal of Gemmology 2014 Vol 34, N°4, p 294-296

Opal

1.45

1.46

2.12

2.16

green, transparent

Zacatecas, Mexico

green daylight luminescing hyalite opal

 

very strong green

very strong green

The Journal of Gemmology 2015 Vol 34, No.6, p486-488

Opal

1.45

1.455

2.05

2.1

greenish-blue

Peru

transparent, dendritic inclusions of manganese oxide

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2016 Jun, p5-6

Opal

1.451

1.459

2.09

2.13

light to medium dark bluish green, opaque to translucent

Haneti, Tanzania

prase opal

broad absorption below 450 and above 650nm

 

 

Gems & Gemology 2009 Winter, p271-279

Opal

1.452

1.452

2.125

2.125

green (prase opal)

Tanzania

 

 

whitish areas : strong to moderate , bluish white

moderate to weak

Gems & Gemology 1984 winter, p226-227

Opal

1.455

1.455

2.18

2.18

yellowish green

Mexico

faceted, 2.30ct, slightly radioactive (0.1 to 0.4mR/hr),

 

extremely strong, bright, yellowish green

extremely strong, bright, yellowish green

Gems & Gemology 1985 Summer, p111

Opal

1.458

1.458

2.08

2.011

 

Pedro II, Piaui, Brazil

 

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1997 Jun, p104

Opal

1.459

1.459

2.15

2.15

yellowish to brownish yellow with dendritic psilomelane inclusions

Lake Kariba,  Zambia

dentritic opal

 

moderate greenish-yellow

moderate yellowish

Zeitschrift der Deutschen Gemmologischen Gesellschaft 1993 Dec, p137

Fire opal

1.459

1.462

2.15

2.18

reddish brown-orange, brownish orange, and brownish yellow

Juniper Ridge, Oregon, USA

1.39 to 5.48 ct

 

very weak chalky green

inert

Gems & Gemology 2003 Spring, p55-56

Opal

1.46

1.46

2.15

2.15

yellow-green

Tsivory, Madagascar

 

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2000 Juni, p85-94

Opal

1.46

1.47

2.32

2.32

blue with play-of-colour

Cosala, Sinaloa, Mexico

"lightning blue opal"

 

strong green

inert

Gems & Gemology 2011 Fall, p243

Opal

1.46

1.46

2.1

2.1

pale, slightly bluish green

Serbia

cabochon, 21.08ct

cut-off edges at 450 and 620 nm

inert

faint chalky green

Gems & Gemology 1995 Fall, p208

Opal

1.46

1.47

2.1

2.13

light green

Serbia ?

5.36 - 17.74ct, cabochons, semi-translucent to translucent

general absorption below 450 nm and above 620nm

very weak green

weak green

Gems & Gemology 2007 Summer, p171

Opal

1.462

1.467

2.241

2.27

light brown, iridescent effect

San Luis Potosi, Mexico

hyalite, "iris opal", transparent

 

 

 

Zeitschrift der Deutschen Gemmologischen Gesellschaft 1989 Aug, p51-62

Opal

1.47

1.47

2.14

2.18

yellowish green to yellowish brown

Brazil

cat's-eye (parallel aranged fibres of chrysotile)

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1996 Mar, p3

Opal

1.475

1.475

2.18

2.25

pink, opaque, cause of colour : organic compounds called quinones

Monte Rosa, Peru

mixture of opal with palygorskite, H : 6

 

inert

weak pinkish white

Gems & Gemology 2006 summer, p176

Opal

1.495

1.495

2.2

2.35

 

Grale of God Mine, Sierra Madre Mts, Sonora, Mexico

 

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 1995 Mar, p5

Opal

 

 

1.4

2

white

Oman

Cascholong opal , hardness 3 - 6

 

 

 

Zeitschrift der Deutschen Gemmologischen Gesellschaft 1993 Dec, p141-148

Opal

 

 

1.65

1.9

white, play of colour

Wegel Tena, Wollo Province, Ethiopia

7-12 ct, high porosity

 

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2010 59/3-4, p65

Opal

 

 

1.91

2.37

pink, green, pale blue, yellowish green, ochre

Acari, Nazca, Peru

opal-C, opal-CT & opal-T

 

 

 

The Australian Gemmologist 2008 Vol 23,N°6, p266-271

Opal

 

 

2.08

2.1

apple green, translucent

border area Croatia-Macedonia

 

bands in the red and violet (due to Ni)

 

 

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2003 Dec, p123

 

TABLES

Stone

RI min

RI max

Dens min

Dens max

Reference

Opal

1.37

1.47

1.25

2.35

Bestimmungstabellen für Edelsteine, Birgit Günther, 2008 

Opal

1.37

1.47

1.25

2.25

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

Opal

1.37

1.47

1.97

2.22

Gemmological Tables, Ulrich Henn, 2004 

Opal

1.37

1.47

1.99

2.25

http://www.gemmology.be 

Opal

1.37

1.47

2.05

2.25

Tabellen zur Edelstein-Bestimmung, Pschichholz FGA, 1975 

Opal

1.37

1.47

1.99

2.25

Joel Arem, Color Encyclopedia of Gemstones, 1987 

Opal

1.37

1.475

1.95

2.25

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

Opal

1.37

1.47

1.25

2.23

Gemology Tools Professional 2010

Fire opal

1.38

1.47

1.25

2.23

Gemology Tools Professional 2010

Opal

1.38

1.47

1.3

2.3

Gemmo.eu 

Fire opal

1.435

1.445

1.97

2.06

John Sinkakas, Gemstone and mineral data book,1972 

Fire opal

1.435

1.455

1.97

2.06

Gems, R Webster, 5th edition 1994 

Fire opal

1.44

1.446

2

2.15

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

Opal

1.44

1.46

1.95

2.2

John Sinkakas, Gemstone and mineral data book,1972 

Opal

1.44

1.47

1.97

2.5

http://www.geminterest.com 

Opal

1.44

1.46

1.98

2.2

Gems, R Webster, 5th edition 1994 

 

CAUSE OF COLOUR

Stone

Colour

Cause of colour

Reference

Opal

blue, greenish blue, green

Cu²+ in form of submicroscopic inclusions

The Australian Gemmologist, 2007, Vol23,N°1,p14

Opal

green

Cr³+

Gemmologie, 1997 Dez, p2-3

Opal

green (prase opal)

microscopic to submicroscopic inclusions of nickeliferous clay like inclusions

Gems & Gemology Summer 1988

Opal

multicolours

diffraction by the regular stacking of silica spheres

Gems & Gemology Summer 1988

fire opal

orange to red

microscopic to submicroscopic inclusions of iron hydrous oxides

Gems & Gemology Summer 1988

Opal

pink

organic compounds, called quinones

Gems & Gemology Summer 2006, p176

Opal

pink

inclusions of cinnabar

Rondeau B. (1998) Origine de la couleur et structure des opales communes, Université de Nantes

Opal

purple

fluorite inclusions

Gems & Gemology Spring 2012, p56-57

Opal

yellow

microscopic inclusions of orpiment

Rondeau B. (1998) Origine de la couleur et structure des opales communes, Université de Nantes

 

MINERAL INCLUSIONS

Inclusion

Stone

Reference

anatase

Opal

Gems & Gemology 2012, Fall, p226

barite

Opal

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

chalcedony

Opal

Gemmological Tables, Ulrich Henn , GGA, 2004

cristobalite

Opal

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

crystobalite

fire opal

Gemmologie, Sep 1997,p167

fluorite

Opal

Gems & Gemology 1983 Summer p94

goethite

Opal

Gemmological Tables, Ulrich Henn , GGA, 2004

hematite

fire opal

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

hornblende

Opal

The Australian Gemmologist, 1986, Vol 16,Nb 2, p49

kaolinite

Opal

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

pyrite

Opal

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

quartz

Opal

Gems & Gemology 1983 Summer p94

zeolite

Opal

Gems & Gemology 2011 Winter, p266

 

LOCALITIES

STONE

LOCALITIES

REFERENCE

Opal

Lightning Ridge

New England District

New South Wales

Australia

Gems & Gemology Fall 2010, p211

Opal

 

White Cliffs

New South Wales

Australia

Gems & Gemology Fall 2010, p211

Opal

Yowah opal field

Eulo (87km)

Queensland

Australia

Lapis 5/1990

Opal

 

Opalton

Queensland

Australia

Gems & Gemology Fall 2010, p211

Opal

 

Quilpie

Queensland

Australia

Le Règne minéral 26/1999

Opal

Stuart Creek Opal Diggings, Stuart Creek

Andamooka Ranges - Lake Torrens area

South Australia

Australia

Gems & Gemology Fall 2010, p211

Opal

Coober Pedy

Coober Pedy

South Australia

Australia

Noble, R.J. (1983)

Opal

Mintabie opal field

Coober Pedy - Everard Range Regions

South Australia

Australia

Gems & Gemology Fall 2010, p211

Opal

 

Lambina

South Australia

Australia

Gems & Gemology 2004 Fall p276

Opal

 

Mintabie

South Australia

Australia

Gems & Gemology Fall 2010, p211

Opal

Boi Morto Mine (Mina do Boi Morto), Pedro II

Piaui

 

Brazil

Gems & Gemology 2002 Fall p268

Opal

Manoel Ambrosio Ranch

Sao Geraldo do Araguaia

Minas Gerais

Brazil

Revista Brasileira de Geociências, vol.30

Opal

Klinker prospect, Vernon

Vernon Mining Division

British Columbia

Canada

Gems & Gemology Fall 2010, p211

Opal

Tsehay Mewcha, Wegeltena, Delanta

Welo (Wello; Wollo)

Afar

Ethiopia

Gems & Gemology Summer 2010, p90-105

Opal

Yita ridge

Mezezo (Mezzezo)

Showa Province

Ethiopia

Gem Information, 23 May 2007 (Japan Germany Gemmological Laboratory), 20-24.

Opal

 

 

Welo

Ethiopia

Gems & Gemology Spring 2009, p59-60

Opal

 

Gracias

Lempira Department

Honduras

N. Jb. Mineral. Abh. 186 (2009) 11-20.

Opal

Kali Maya

Banteen Province

Java

Indonesia

Extra Lapis - English No. 10 Opal

Opal

 

110km NW of Sharh-e Babak

Kerman Province

Iran

Gems & Gemology 2007 fall, p257

fire opal

 

Aleksejewskoje

 

Kazachstan

Zeitschrift der Deutschen Gemmologischen Gesellschaft, 1991, Apr p11-23

fire opal

Bemia

Befotaka

Fianarantsoa Province

Madagascar

Gems & Gemology 2010 Summer, p114-121

fire opal

 

Beraketa

Tuléar (Toliara ) Province

Madagascar

Gemmologie, Dez 1999,p196

Opal

 

Nioro du Sahel

Kayes Region

Mali

Gemmologie, Zeitschrift der Deutschen Gemmologischen Gesellschaft 2013 62/1-2, Jun, p46-48

Opal

Leopard opal deposit, 14km South of Zimapan

Zimapan

Hidalgo

Mexico

Gems & Gemology 2006 Winter p 238

Opal

 

Cosala

Sinaloa

Mexico

Gems & Gemology 2011, Fall, p243

Opal

Monte Rosa Mine

Ica Department

 

Peru

Extra Lapis - English No. 10 Opal

Opal

Acari mine

Nazca

Arequipa Department

Peru

Hyrsl & Rosales (2003), Min. Record 34:254

Opal

 

Hanety Hill (Haneti)

 

Tanzania

Gems & Gemology 2009 Winter, p271

Opal

 

Claiborne County

Mississippi

USA

Journal of the Mississippi Academy of Sciences, Jan. 2004.

Opal

Virgin Valley District

Humboldt County

Nevada

USA

Minerals of Nevada, Stephen B. Castor and Gregory C. Ferdock, 2004

fire opal

Juniper Ridge Opal Mine

Lake County

Oregon

USA

Extra Lapis - English No. 10 Opal

Opal

Opal Butte

Morrow County

Oregon

USA

Gems & Gemology 1988 winter

 

CHEMICAL DATA (%)

Stone

Colour

Locality

Reference

SiO2

Al2O3

MgO

TiO2

CaO

Na2O

Fe2O3

K2O

Cs2O

H2O

Opal

blue

 

 

The Journal of Gemmology 2000, Vol 27, N°5,p282

98.71

0.1

0.03

0.01

0.33

0.73

 

0.09

 

 

Opal

yellowish green

 

Madagascar

Gemmologie, Zeitschrift der deutschen gemmologischen Gesellschaft, 2000, Jun, p89

92.79

2.06

0.1

 

0.18

0.06

0.5

0.1

 

3.5

Opal

yellowish green

 

Madagascar

Gemmologie, Zeitschrift der deutschen gemmologischen Gesellschaft, 2000, Jun, p89

94.1

1.02

 

 

0.12

 

0.25

 

 

3.5

Opal, hyalite

light brown

San Luis Potosi

Mexico

Zeitschrift der Deutschen Gemmologischen Gesellschaft, 1989, Aug, p51-62

87.9

3.64

 

 

 

0.55

 

1.93

2