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
Foreword	vii
Preface	ix
1. Getting Started	1
Buying Opal	1
Valuing Opal	2
Opal Myths	3
2. About Opal	5
What Is Gem Opal?	5
Types of Opals	6
The Source	6
Cutting Opal	7
What Makes a Good Opal?	8
3. Identifying Type	11
Types of Opal	11
Determining the Type of an Opal	14
Identifying Set Stones	20
Importance of Type	21
Summary	22
4. Natural, Synthetic, Simulant, Dyed	25
Synthetic	25
Simulants or Imitations	26
Dyed Opal	28
Conclusion	30
Summary	30
5. Base Color	31
What is Base Color?	31
Definitions of Base Color	33
Determining Base Color	35
Black Opal Criteria	36
Crystal and Semi-Crystal Criteria	40
Base Color and Value	42
Summary	43
6. Brightness of Fire	45
Brightness Standard	45
Light and Brightness	47
Developing Brightness Criteria Stones	48
Judging Brightness	50
Brightness is Most Important	51
Summary	52
7. Fire Color	53
Dominant Color	53
The Multicolor Rule	56
Hue, Saturation and Intensity	57
Judging Fire Color	58
Summary	58
8. Fire Pattern	59
Patterns Defined	59
Harlequin Pattern	61
Rare Patterns	62
Picture Stones	66
Determining Pattern	67
Summary	68
9. Consistency and Directionality	69
Consistency	69
Directionality	70
Summary	71
10. Cut, Inclusions and Weight	73
Cut	73
Weight and Thickness	75
Weight and Thickness in Calibrated Oval Opals	77
Inclusions	79
Cracks and Crazing	79
Stability	81
Weight	83
Cut, Inclusions, Cracks and Value	84
Summary	84
Weight Estimation Formula Supplement	86
Weight Estimation	86
Standard Shaped Cabochons	86
Example	87
Bulge Factor	88
Freeform Stones	89
11. Properly Set Opals	91
Protecting the Opal	91
Custom Designers	93
Sizing Rings	95
Inlayed Opal	96
Summary	97
12. Solid Opal Prices	99
Opal Prices	99
Estimating Price	102
Example	106
Summary	109
Characteristics Adjustment Supplement	110
Price Adjustments	110
13. Boulder Opal Prices	117
Types of Boulder Opal	118
Characterizing Boulder Opal	120
Pricing Boulder Opal	124
Example	126
Pricing Boulder Matrix	128
Andamooka Boulder	129
Conclusions	129
Summary	129
Boulder Adjustment Supplement	130
14. Other Opal Prices	133
Pricing Doublets	133
Triplet Prices	136
Summary	141
15. American and Canadian Opal	143
American Opal	143
Nevada Opal	143
Idaho Opal	145
Oregon Contra Luz	146
Arizona Blue Opal	148
Louisiana Opal	148
British Columbian Opal	148
Summary	150
16. Other Locations	151
Mexican Opal	151
Brazilian Opal	154
Honduras Opal	155
Indonesian Opal	156
Ethiopian Opal	156
Summary	157
17. Opal Jewelry	159
Commercial Settings	159
Manufactured Jewelry	160
Designer Jewelry	160
Designer One-of-a-Kind	161
Antique / Estate Jewelry	162
Opal Design Treatments	172
Summary	178
18. Collections and Carvings	179
Collector Pieces	179
Fossils	182
Carvings	183
Summary	185
19. Buying Opal	187
Finding Opal	187
Buying Opal	189
Buying in Australia	191
Summary	192
20. Conclusions	193
Glossary of Terms	195
Index	200
Acknowledgements	205
Photographers	206
Designer Contacts	207
Other Books By Paul B. Downing	208
About the Author	212