Gemstone Value Comparison Charts
The charts on pages 136 and 137 (Next Chapter) show the value references for 44 types of gemstones. They are intended to give an overview of the differences in the relative values between these gems. Comparing, for example, the value indexes for 10-carat-size gem-quality gemstones, untreated Mogok ruby is 12,000, aquamarine is 120, and citrine is 12. Even at the same 10-carat-size, there can be a hundred-or thousand-fold difference in value, depending on the type of gemstone.
Using the value of a one-carat-size, jewelry-quality round brilliant diamond as a reference of 100, the charts compare the three qualities of each gem in three sizes (10, 3, and 1 or 3, 1, and 0.5 carat-sizes). These indexes are based on 2001 market prices. The quality scales for all but two of the 44 gemstones indexed have bee printed in this book and my previous Gemstones: Quality and Value, Volume 1. Kashmir sapphire is extremely difficult to obtain, while blue zircon was omitted due to space limitations. Please accept my apologies for this.
From each quality scale, a median point was assumed and the various value reference indexes were built around these. While some gem-quality stones of exceptional value may have a value ranging from two times to as much as five times what is shown in the index, some accessory-quality stones only have a value close to the cost of polishing, due to a lack of beauty or conspicuous defects.
Twenty-seven of the gemstone types listed, including the various diamonds types, are stones that normally do not require treatment. The emeralds, rubies, and sapphires fashioned from high-quality rough without treatment are noted in the charts as untreated (N). Of the eleven gemstones that are heat-treated (H), aquamarine, pink topaz, green tourmaline, and amber may also be untreated, but there is no common practice of separating or nothing this. Colombian and Zambian emeralds are usually fracture-filled (impregnation-treated) with oil or resin, and turquoise is often impregnated with acrylic resins to enhance its color and / or prevent discoloration. These are collectively noted as impregnated (I). Jadeite is often waxed after polishing as a finishing step to improve the luster of its surface, but because this does not significantly affect quality, jadeite is listed as untreated (N).
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There is a need for continuing observation to see how the market will react to issues such as high-temperature heat treatment and its effects on durability in Mong Hsu rubies, or the deterioration of oil and polymer treatments in low-quality materials, and how these will influence value in the future. |
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Sample Auctions
Hammer Prices
Occasionally tow or three private patrons at an auction will bid against each other and raise the price of an item to as much as three times the estimated hammer price. This is a tribute to the extremely beautiful, defect-free, and very rare nature of the gemstone-oriented jewelry piece in question. A high price is not a guarantee of fine quality, but high-quality gemstones will always command a high price.
1.
13 November 1995
Christie’s, Geneva
Pear-shaped diamond, 16.66 carats (D-VS1)
Ring by Van Cleef and Arpels
Total Price: US $1,755,310
(US $105,360 per carat)
This diamond was accompanied by working diagram stating its potential of achieving a clarity grade of Flawless(FL) if recut.
2. 21 November 1996
Christie’s, Geneva
Ring containing a rectangular Colombian emerald, 10.35 carats, and 12 diamonds (all 1-carat-size, gem-quality, pear-shape)
Total Price: US $733,200
Emerald price estimated at US $600,000 (US $58,000 per carat)
This emerald was accompanied by a grading report from the Swiss Foundation for the Research of Gemstones (SSEF) stating that there was “no presence of filler.” This price was driven up by the fact that the stone was an untreated Colombian emerald.
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