Table of Contents
1. Exotic Gems 9
2. Price Factors in a Nutshell 12
Price Factors Explained 12
Color 12
Clarity 14
Transparency 17
Shape 18
Cutting Style 18
Cut Quality 18
Brilliance 19
Carat Weight or Stone Size 20
Treatment Status 20
Copper, Chromium and/or Vanadium Content 20
Geographic Origin 20
Distinctness of Optical Effects (Phenomena) 21
Colored Gem Pricing 22
3. Tourmaline Group 23
A Brief History of Tourmaline 23
What is Tourmaline? 27
Identifying Tourmaline 28
Tourmaline Chemistry 29
Tourmaline Species Characteristics in Brief 31
Tourmaline Varieties 33
How a Master Cutter Cuts a Tourmaline 34
Cutting Tourmaline (by John Bradshaw) 38
Caring for Tourmaline 38
4. Paraiba & Other Copper Tourmalines 39
What is a Paraiba Tourmaline? 42
Identification of Cuprian Tourmaline 45
Price Factors for Copper-Bearing Tourmaline 47
Alternative Terms for “Paraiba” 48
5. Blue to Green Tourmalines 49
What is Indicolite? 49
What is Chrome Tourmaline? 50
Verdelite or Green Tourmaline? 52
Blue-green Tourmaline 55
Gray Tourmaline 56
Identifying Green Tourmaline 57
6. Pink & Red Tourmaline 58
What is Rubellite? 60
Evaluating Pink & Red Tourmaline 63
Sources of Pink & Red Tourmaline 64
7. Yellow, Orange & Brown Tourmalines 66
8. Multicolored Tourmalines 70
Formation of Multicolored Tourmaline 72
Liddicoatite 73
Effect of Color Zoning on Pricing 74
Pleochroic Multicolor Effect 74
Multicolored Tourmaline Jewelry 75
9. Cat's-eye & Color-change Tourmaline 79
Color-change Tourmaline 81
10. Blue Chalcedony 86
What is Chalcedony? 88
Identifying Blue Chalcedony 90
Geographic Sources of Blue Chalcedony 91
Judging Blue Chalcedony Quality 97
Caring for Blue Chalcedony 98
11. Fire Agate 99
Fire Agate Price Factors 101
Cutting Fire Agate 104
Caring for Fire Agate 108
12. Matrix Opal 109
Boulder Matrix Opal 112
Andamooka Matrix Opal 120
Honduras Matrix Opal 122
Mexican Matrix Opal 124
Identifying Traits of Opal 125
Pricing and Evaluation of Matrix Opal 127
Caring for Matrix Opal 130
Bibliography 131
Index 134