Perfection in a diamond is measured precisely by its carats, clarity, cut, and color — the famous “four Cs.” When it comes to colored diamonds, however, one must add intensity and purity of hue. The matrix of these qualities is used to determine a stone’s value. While the possible combinations are virtually infinite, the official vocabulary used to describe and certify these gems is not, and two dissimilar-looking diamonds can bear the same grade. Consumers need to educate themselves so they can be sure they’re not “buying paper.” (As Henri Barguirdjian, president and CEO of Graff Diamonds USA, says, “A little knowledge is dangerous.”) Here’s how to read between the lines.
ONE IN A MILLION
Fine-quality colored diamonds are truly rare. A typical mine will produce one colored diamond for every 10,000 white or colorless stones, but only one large, fine, fancy colored diamond will be found for every million mined. Some colors are the result of trace elements or minerals — blue diamonds, for example, get their hue from boron, while nitrogen produces yellow diamonds. Green diamonds are exceedingly rare and the only kind to get their color from natural radiation in the earth. Pink is the result of a “deformation of the stone’s internal structure,” says John King, chief quality officer for the Gemological Institute of America (GIA), the dominant diamond-certifying laboratory in the United States. Cutters attempt to coax maximum color from the natural material, known as rough, and it’s a delicate dance. According to King, “The orientation of the rough during polishing can make a difference in the internal reflections and refractions.”
Colored diamonds rarely occur in unmodified tones; that’s why the purest pinks, yellows, and blues are considered the most valuable. Descriptive modifiers are applied according to the proportion of each color in the stone. For example, a diamond that combines yellow and orange tones might be described as yellowish-orange, yellow-orange, orange-yellow, or orangey-yellow, depending on the extent of the orange tint. The GIA uses 27 standard hue names as a guide to describing colors in diamonds, but recognizes that there are at least 270 variations when modifiers are factored in.
GETTING IN DEEP
Unlike flawless D-grade whites, when it comes to colored diamonds, intensity rather than absence of hue wins the prize. Along with describing a color, the GIA grades its saturation using the following nomenclature: faint, very light, light, fancy light, fancy, fancy dark, fancy intense, fancy deep, and fancy vivid. The last two designations were added in 1994 to reflect the broader range of shades coming to market. The array is widest for yellow diamonds, the most numerous type by far. And these differences are not just semantic. A stone’s value can increase by as much as 25 percent for each notch it moves up on the saturation scale.
PINK IS PRIME
The color pink has universal appeal, and it has become the most sought-after color in the current market thanks to headline-grabbing prices, such as the $46.3 million paid at Sotheby’s Geneva in November 2010 by jeweler Laurence Graff for a 24.78-carat fancy vivid pink. Citing the 9-carat Clark Pink and the 12-carat Martian Pink that Christie’s sold in Geneva and Hong Kong, respectively, last spring, Rahul Kadakia, head of jewelry for Christie’s Americas, says, “Exceptional gems undoubtedly attract new collectors at the highest level.” Interest is global: New buyers from the Middle East, Russia, and Asia are competing for the very few pink stones that come on the market each year, whether from estates or mines.
Outside of the stratosphere, prices are still highly dependent on the individual stone. A three-carat, high-clarity fancy yellow diamond without modifiers might be sold by a dealer for $8,000 to $9,000 per carat. The same color and clarity in a five-carat stone would command $12,000 to $14,000 per carat, says Elan Ben-David, of fancy colored diamond specialists Ishay Be David.
Even with two major pinks on the market right now — a 12.27 carat fancy pink, VVS1 clarity stone offered by M.S. Rau Antiques in partnership with 1stdibs, priced at $7,850,000, and a 10.15-carat rock (est. $HK18–23 million; $2.3–3 million) to be offered at Sotheby’s Hong Kong on the 9th of this month — large, fine-quality pink diamonds are extremely rare. At this level, the only guideline for price is the eagerness of the market.
- Expertise in cutting is crucial to all colored diamonds. Poor choices can lead to loss of some of the inherent color.
- As with colorless diamonds, clarity is judged by the number of inclusions, or flaws visible at 10-power magnification. Stones showing no inclusions whatsoever are rated flawless or internally flawless; the latter term applies if there is minor surface damage. The next top grade is VVS1, followed by VVS2, both indicating minimal inclusions, and moves down the scale through VS1, VS2, SI1, SI2, I1, I2, and I3.
- Diamonds are classified by their carbon makeup as Type I or Type II, with sublevels for each. Almost all fine colored diamonds are type II, having no measurable nitrogen impurities, and are the result of higher pressure over a longer time period.
- Any stone with documentation dated prior to 1994 should be recertified before sale, as saturation ratings by the gIa have changed. In the past, a stone could be described as simply “blue,” but today it might be “intense blue” or “vivid blue.”
This article appeared in the October 2012 issue of Art+Auction.