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Opal Identification and Value


If you want to learn about opal, this is the book. It's our favorite book about opal. It clearly describes the many different types of opal in language that is easy to understand. Includes information about how opal is identified, valued, mined, cut and used in jewelry. Explains natural, synthetic, simulant, and assembled stone types. This book is a 6 1/2" x 9 1/4" hardcover with 212 pages.

Opal Identification and ValueTable of Contents

Forewordvii
Prefaceix
1. Getting Started1
Buying Opal1
Valuing Opal2
Opal Myths3
2. About Opal5
What Is Gem Opal?5
Types of Opals6
The Source6
Cutting Opal7
What Makes a Good Opal?8
3. Identifying Type11
Types of Opal11
Determining the Type of an Opal14
Identifying Set Stones20
Importance of Type21
Summary22
4. Natural, Synthetic, Simulant, Dyed25
Synthetic25
Simulants or Imitations26
Dyed Opal28
Conclusion30
Summary30
5. Base Color31
What is Base Color?31
Definitions of Base Color33
Determining Base Color35
Black Opal Criteria36
Crystal and Semi-Crystal Criteria40
Base Color and Value42
Summary43
6. Brightness of Fire45
Brightness Standard45
Light and Brightness47
Developing Brightness Criteria Stones48
Judging Brightness50
Brightness is Most Important51
Summary52
7. Fire Color53
Dominant Color53
The Multicolor Rule56
Hue, Saturation and Intensity57
Judging Fire Color58
Summary58
8. Fire Pattern59
Patterns Defined59
Harlequin Pattern61
Rare Patterns62
Picture Stones66
Determining Pattern67
Summary68
9. Consistency and Directionality69
Consistency69
Directionality70
Summary71
10. Cut, Inclusions and Weight73
Cut73
Weight and Thickness75
Weight and Thickness in Calibrated Oval Opals77
Inclusions79
Cracks and Crazing79
Stability81
Weight83
Cut, Inclusions, Cracks and Value84
Summary84
Weight Estimation Formula Supplement86
Weight Estimation86
Standard Shaped Cabochons86
Example87
Bulge Factor88
Freeform Stones89
11. Properly Set Opals91
Protecting the Opal91
Custom Designers93
Sizing Rings95
Inlayed Opal96
Summary97
12. Solid Opal Prices99
Opal Prices99
Estimating Price102
Example106
Summary109
Characteristics Adjustment Supplement110
Price Adjustments110
13. Boulder Opal Prices117
Types of Boulder Opal118
Characterizing Boulder Opal120
Pricing Boulder Opal124
Example126
Pricing Boulder Matrix128
Andamooka Boulder129
Conclusions129
Summary129
Boulder Adjustment Supplement130
14. Other Opal Prices133
Pricing Doublets133
Triplet Prices136
Summary141
15. American and Canadian Opal143
American Opal143
Nevada Opal143
Idaho Opal145
Oregon Contra Luz146
Arizona Blue Opal148
Louisiana Opal148
British Columbian Opal148
Summary150
16. Other Locations151
Mexican Opal151
Brazilian Opal154
Honduras Opal155
Indonesian Opal156
Ethiopian Opal156
Summary157
17. Opal Jewelry159
Commercial Settings159
Manufactured Jewelry160
Designer Jewelry160
Designer One-of-a-Kind161
Antique / Estate Jewelry162
Opal Design Treatments172
Summary178
18. Collections and Carvings179
Collector Pieces179
Fossils182
Carvings183
Summary185
19. Buying Opal187
Finding Opal187
Buying Opal189
Buying in Australia191
Summary192
20. Conclusions193
Glossary of Terms195
Index200
Acknowledgements205
Photographers206
Designer Contacts207
Other Books By Paul B. Downing208
About the Author212