A JOURNEY WITH COLOUR, Vol I & II, Len Cram (Photos: various patterns)

AUSTRALIAN PRECIOUS OPAL, Archie Kalokerinos, 1971.(Photos:Hexagonal Harlequin, Pinfire)

AUSTRALIAN PRECIOUS OPAL, Andrew Cody, 1991. (Photos: Brilliance Scale)

OPAL IDENTIFICATION AND VALUE, Paul Downing PhD., 2001.

Crystal, Boulder and Black Gems from the Opaline Collection

A NEW ERA FOR NOMENCLATURE, Australian Gemmologist. 19, 486-496., Anthony G. Smallwood, 1997.

OPAL MODULE, GAA COURSE NOTES, Anthony G. Smallwood, 1998.

THE SMART CHART, Peter Evans, 2005.

NCJV OPAL GRADING & PRICING WORKSHOP, Ralph Pownall, 2011.

Click here to download the pdf of the Opal Body Tone and Patterns Chart (courtesy of Opal Association - www.opal.asn.au)

Sources : 

"Opal in South Australia", Mines & Energy Resources, SA

"Opal", Qld Dept. of Mines & Energy

"Black Opal: A comprehensive guide to cutting and orientation", by Greg Pardey, GP Creations, 1999.

Click here to download the pdf of the Opal Body Tone and Patterns Chart (courtesy of Opal Association - www.opal.asn.au)

Sources : 

"Opal in South Australia", Mines & Energy Resources, SA

"Opal", Qld Dept. of Mines & Energy

"Black Opal: A comprehensive guide to cutting and orientation", by Greg Pardey, GP Creations, 1999.

"Opals", by Fred Ward, Gem Book Publishers, 1997.