Reference:
ABOUT OPALS
What is a Crystal Opal ?
Opal shows all forms of diaphaneity that range from transparent to opaque. Natural precious opal which is transparent to semi-transparent is known as crystal opal (Figs. 11A-C). Crystal opal can have either a black, dark or light body tone. In this context, the term ‘crystal’ refers to the appearance of the opal and not its crystalline structure.
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Fig. 11A |
Fig. 11B |
Fig. 11C |
Crystal opal |
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Transluscent appearance - a printed page would be roughly visible through the stone. Relatively abundant. |
Most opal fields |
Find more information at the OPAL Associations Opal Nomenclature Section of their Website:
http://www.opal.asn.au/information_nom
