A Review of the mineralogical opal classification

Neville Curtis and colleagues discuss an update from their investigations and experimental data for the mineralogical aspects of Opal-A (Opal-AG, Opal-AN), Opal-CT and Opal-C by X-ray Diffraction, Infrared Spectroscopy, Raman Spectroscopy and NMR (Nuclear Magnetic Resonance. The group analysed over 230 opal samples from world wide sources.

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Tully Wollaston
Tully Wollaston

An Extract from Len Cram’s a journey with colour

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Chemistry Techniques used in researching opal - Neville Curtis
Chemistry Techniques used in researching opal - Neville Curtis
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A discussion on Ethiopian Opal from our french colleagues.
A discussion on Ethiopian Opal from our french colleagues.

AN article written in French from our colleagues in the French Gemmological Association

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African Opal Unearthed
African Opal Unearthed

Paul Downings article on Ethiopian Opal

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Play-of-Colour Opal from Wegel Tena, Wollo Province Ethiopia
Play-of-Colour Opal from Wegel Tena, Wollo Province Ethiopia

A journal article from Gems and Gemmology on the occurrence of Precious opal in Ethiopia

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The Origin of Digit patterns
The Origin of Digit patterns

AN article regarding the special digit patterns in Ethiopian Gem opal

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Ethiopia: A new source of Precious Opal
Ethiopia: A new source of Precious Opal
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WHITE CLIFFS-CRAM
WHITE CLIFFS-CRAM

An excerpt of the history of White Cliffs

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The White Cliffs Royal Commission
The White Cliffs Royal Commission

The White Cliffs Royal Commission

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White Cliffs Opal Field- A report by NSW Geological Survey
White Cliffs Opal Field- A report by NSW Geological Survey

Quarterly Notes NSW Geological Survey-White CLiffs

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White Cliffs Opal Fields a commentary by Gwen Rowe
White Cliffs Opal Fields a commentary by Gwen Rowe

A view of the town of White Cliffs

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OPAL CARVING-DANIELA L'ABBATE
OPAL CARVING-DANIELA L'ABBATE

Daniela L’Abbate, specialist opal carver.

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EVALUATION OF CARVED LIGHTNING RIDGE BLACK OPAL
EVALUATION OF CARVED LIGHTNING RIDGE BLACK OPAL

Information and procedures for valuing carved opal

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HISTORICAL FOLKLORE-KOSMINSKI
HISTORICAL FOLKLORE-KOSMINSKI

An extract of the chapters relating to opal

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Trace Elements in Black Opal
Trace Elements in Black Opal

A discussion paper form Bruce Dickson regarding trace elements in Australian black opal

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More on opal and cracking
More on opal and cracking

Boris Chauvire and colleagues elucidate some information regarding opal cracking

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New information - Slovakian opal
New information - Slovakian opal

An updated article regarding Slovakian Precious opal jewellery

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Porosity of some opaline siliceous materials
Porosity of some opaline siliceous materials

A discussion on the porosity of siliceous materials including opal

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The Role of water in the cracking of opal
The Role of water in the cracking of opal

A discussion from the Australian Gemmologist regarding opal cracking

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AN Historic document: the Occurrence of Opal at Lightning ridge and Grawin.
AN Historic document: the Occurrence of Opal at Lightning ridge and Grawin.

An historical discussion of the geology and occurrence of opal at Lightning Ridge

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An analysis of Opal Polymorphs: Opal-AG, Opal-AN and Opal-CT by NMR
An analysis of Opal Polymorphs: Opal-AG, Opal-AN and Opal-CT by NMR

An analysis of opal polymorphs by NMR

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A Review of the mineralogical opal classification
A Review of the mineralogical opal classification

In this Article, Neville Curtis and his colleagues discuss new information regarding the mineralogical varieties of opal

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SYNTHETIC OPAL
SYNTHETIC OPAL

A micrograph of the pattern so called “lizard skin” of synthetic and imitation opal

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Trace Elements in Australian Opal-1
Trace Elements in Australian Opal-1

Trace Elements - 1

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Historical opal literature - an extract from Dana's Mineralogy
Historical opal literature - an extract from Dana's Mineralogy

the following document is an extract of the opal pages from Dana’s Mineralogy

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An Extract from the Thesis of Boris Chauvrie
An Extract from the Thesis of Boris Chauvrie
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GILC and LMHC decisions for Hydrophane opal nomenclature
GILC and LMHC decisions for Hydrophane opal nomenclature
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Opal Historical SA Trade standards (1979)
Opal Historical SA Trade standards (1979)

The article in this issue of the Australian Gemmologist was for its time a ”land breaking” discussion on opal nomenclature.

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Opal Nomenclature - AG1997
Opal Nomenclature - AG1997

The article in this issue of the Australian Gemmologist was for its time a ”land breaking” discussion on opal nomenclature.

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The Story of European Precious opal from Dubnik
The Story of European Precious opal from Dubnik
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Anthony Smallwood