These three gems may not be the same size originally, but I took care to reproduce their photos to scale them to the same 32mm diameter on a 100dpi screen. That is about a 4x magnification for a 1 carat stone. Gemstones are rated under 10x magnification, and if no flaws are visible at 10x, the stone is pronounced "flawless", even though flaws might become evident under greater magnification. These three images show a few things about a gem's value. First, on the left, we see a stone that is losing some light out of certain pavilion (back) facets. It was cut a little too shallowly, which makes a larger stone at a certain weight, but detracts from the brilliance of the stone. The central image is of a properly cut stone (not just because it was photographed with a white background). The image on the right is not a diamond, but is Moissanite, a lab-grown, clear silicon carbide gemstone. With a higher refractive index and 2.5 times the spectral dispersion, Moissanite looks like an overdone diamond. Its value per carat, however is quite a bit less than a flawless white diamond.Diamond value is traditionally based on four C's: Carat weight, Color, Clarity and Cut. A 1-carat stone of excellent cut may be worth $20,000-30,000 if it is entirely white ("D" color) and flawless, but a diamond you or I could afford, in the $2,000 range, will be very slightly yellow ("H" or "I" color) and have a tiny feather or speck over to one edge, not visible without magnification, but quite evident under 10x. Strange to say, there is a "valley" in value for stones of color "I" to about "T", then yellower stones, called "canary" if yellow or "chocolate" if more brownish, start to command a premium as "fancy" varieties.
I have a friend who used to travel about selling gemstones to jewelry stores, but only "colored" stones. He did not sell diamonds, because it is a very hard business to break into. Also, because of the over-hyped glamor of diamonds, it is a lot more risky to carry them around. Even so, he got out of the business when a bag of merchandise was stolen from his car. He lost $70,000.
Alicia Oltuski has an entree into the diamond business, having a father and grandfather who trade in diamonds and diamond jewelry. She let herself be drawn partway into the business, but mainly to gather information to write her book Precious Objects: A Story of Diamonds, Family and a Way of Life. She opens the book with her own experience carrying a chest pack containing a few thousand dollars worth of merchandise to an associate's office. She closes by telling of her father's help, a few weeks prior to her courier experience, when she was getting her engagement diamond reset into a new setting.
In between, she delivers a touching and fascinating memoir of the family business in the Diamond District of Manhattan's 47th Street, near Fifth Avenue. It really is true that most (but not all) of the diamond dealers are Hasidic Jews. Quite a number are Jews, but not Hasids, but a growing number are from India or are Muslim. For some reason, you just won't find many WASPs in the diamond business. Until recently, it was hard to do business there if you didn't speak Yiddish.
The book tells the intertwined stories of the men (and a very few women) who wholesale the stones and of the diamonds and an industry that grew up around a deliberate monopoly to enhance their value. From crafting the slogan "Diamonds are a girl's best friend" to the stockpiling of excess stones when prices fall, the deBeers company and its allies pretty much created value for a material that is much less rare than, for example, high quality ruby or emerald.
Nonetheless, there is a certain aura about this "coal that made good", for diamond is pure carbon; a certain cachet about the most strongly refractive natural material. The term "adamantine luster" is reserved for the way an uncut diamond looks when cleaned off. It looks more like a piece of metal than a transparent material ought to. That is because, with a refractive index of 2.42, diamond reflects 17% of the light that strikes it, as compared to 3%-5% for most kinds of glass and 3.5% for quartz. (Note: silver's reflectivity of 95% implies a refractive index near 80).
In a shop where diamonds are cut into gemstones, the dust is black, further evidence that this is carbon we are working with. The heat and stress of abrading material from a diamond causes the dust to revert to graphite. Only a diamond can cut diamond, so the grinding and polishing wheels are charged with diamond grit and diamond "flour", respectively. This material, four times as tough as sapphire, makes a lot of noise when it touches the wheel, though Ms Oltuski didn't mention whether diamond cutters lose their hearing.
A major section of the book details the way stones are valued and evaluated. The GIA (Gemological Institute of America) now grades most stones larger than a half carat or so, and trains (for a fee) diamond dealers and jewelers in the niceties of evaluating color and clarity. Color is more subtle than we usually imagine. The difference between the whitest stone, "D" in color, and a "G" colored stone, is almost impossible for most of us to discern. Properly trained, a jeweler can distinguish "D", "E", "F", and "G" and so forth, from one another.
Seeing inclusions is one thing. At 100x, no diamond is without some imperfection. But at 10x, at least a small percent are without visible flaw. When there is a flaw, is it central (very bad) or near an edge or corner of the stone? Is it a slight "feather" or a black blot (a chunk of coal caught up in the stone)? Clarity grading is almost alchemical in its arcane intricacies. One clue we learn from the author's father: he first examines a stone at 16x. This makes more imperfections visible. Then he uses 10x, to see if any are still visible. He can then focus on any that are still evident and more fairly grade the stone. One must be careful with such knowledge. I once ruined my sister-in-law's day when I applied a 20x loupe to her engagement ring and showed her the little feather near one edge. Under 10x I couldn't see it, and neither could she, but she was now suspicious that the stone wasn't really "flawless". I shoulda kept my big mouth shut.
Concealment of knowledge becomes second nature to a gem dealer. Mr. Oltuski, if asked, says he is a businessman, or a merchant, without ever letting an acquaintance draw out just what his merchandise is. He might carry about a fortune in stones in an old, taped-up backpack, but he prefers a smaller, under-the-coat chest pack. In more recent years, he won't carry his own stones at all, if he is transporting a large amount, to a show for example. He'll hire Brinks or another armed courier service to carry the merchandise. Yet the trading back and forth between dealers on 47th Street is still usually done using small envelopes, with nothing more than a handshake and a word or two of agreement to set up or seal a deal.
All that may be coming to an end. The Diamond District arose less than eighty years ago, and the newer generation of dealers uses the Internet more, spends little time in musty shops, and cares less for the mystique that absorbed the past two generations. A portion of the old district is being rebuilt into a few large buildings, and the GIA is planning to move into one of them. Among a couple thousand diamond dealers, some are retiring without a successor, so either a fellow dealer (or a group of them) will buy out the retiree's shop, or someone like "Johnny Buyout" will glom onto an entire shop's stock and parcel it out, high, low and middle, wherever it will sell the best.
I can't close without mentioning the chapter on efforts to stem the trade in "blood diamonds". With great effort, nearly all stones are now kept traceable to the district or mine from which they came, which has pinched off the river of profit that many African insurgencies fed from. The matter is not yet ended, but the early years of the 21st Century, with the emphasis on tracing everything, has made such work easier, and it will become easier yet. Who knows: Diamond is not only a great insulator, it can be made into a semiconductor, and it is quite possible that soon, one girdle facet of every diamond will be "doped" into a little RFID device so a diamond can literally tell you where it came from.
I bought a diamond ring for a girl once. When the engagement faltered, she did not return the ring. She pawned it. Fortunately, the lesson was not lost on me. I found a different kind of woman. My wife has no diamonds, but even though she cares nothing for jewelry (such creatures do exist!), she is a keeper, for 37 years now. Would she be a better wife with a half-gram rock on her finger? Knowing her, she wouldn't wear it anyway. So, though I am a geologist and a rockhound, I look at the gemstone world from the outside. I admire stones for their intrinsic qualities. A diamond is a mineral, a particularly lovely one. But I'd rather have a small, well-formed uncut crystal than a "rock on a ring". What I do value is the writing of a sensitive author about a world that is vanishing, and the people who inhabit it still.
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