How to Buy a Diamond
By John Donivan
Probably every adult has heard of "The Four C's". They are Color, Clarity, Cut and Carat Weight. I'll try to walk you through what they all mean here, and hopefully clarify the concepts. Taking the last, Carat Weight, first - It simply means that bigger diamonds cost more. Diamonds are bought and sold by the carat. The carat is a metric weight that equals 1/5 gram, or .2 grams, or 200 milligrams. Plus a carat is divided into a smaller divisions which are called "Points". There are 100 points to one carat. Therefore a half carat diamond weighs 50 points, which is usually expressed as .50 ct. What the Weight thing really means is that larger stones are more rare, so, while you might pay $2000 per carat for a half carat stone, you will pay $4000 per carat for a 1 carat stone. When you do the arithmetic: $2000 per ct. x .50 (1/2 ct.) = $1000 for the stone, that's called the "net price". However, it is much more useful to think of the "Per Carat" price, because then you can compare stones. Example: This stone weighs 1.35 cts (one carat and 35 points) and costs $6500 per carat. This other stone weighs 1.28 cts. and costs $5800 per carat. Why? Sometimes stones just are a better deal, but more often there's a reason relating to the other three C's.
Here's how the diamond business traditionally works: The miners take the rough out of the ground, sort them and grade them, and then they hold "Sights". High volume dealers and cutters are offered parcels of rough stones. The important thing to know is that they are generally offered comparable goods for the same price. They buy the stones and take them home and cut them, or sell off some of them. The important thing to know is that their cutting costs are going to be roughly the same for a comparable quality of labor, and that it is the cutting of a stone that represents most of the cost of a diamond. Then they will offer the finished goods for sale, again with roughly the same markup as their colleagues. What all this means to you, the consumer, is that all diamonds cost the same price, in a general way. It's not exactly true, but the point is that if you are offered one stone for $5,000, and another for $3,500, and they are the same weight, it is much more likely that there is a reason than that somebody is giving away a diamond or they like your looks. You are probably being offered a stone that's worth $5,000, and another that's worth it's price - $3,500, for whatever reason. If it seems too good to be true, it probably is.
The first "C", color, is one of the most important to understand. When the modern system of grading was devised, it was decided to not use "A, B, or C", because of the preexisting associations people have with those, so color grading begins with "D", and goes to "Z". Although people call diamonds white, they are actually, of course, clear or colorless. The color grade is based on the amount of yellow in the stone. There are other colors in diamonds - blue, red, green, and more commonly, brown. If the color present is anything other than yellow, it is inappropriate to use the letter grading system. So brownish diamonds are called "top light brown", light brown, brownish and the like. Color in diamonds is assessed with the stone upside down, looking at the bottom of the diamond. The color in gemstones is called "body color", and looking at a diamond in this way let's one see the body color, without the refraction and scintillation on the top of the stone. Although an expert diamond grader can often give a good stab at the color of a stone when it is "Face Up", as when it's set in a ring, it cannot be truly graded that way. A "D" color diamond is crystal clear, like looking into mountain spring water, without a trace of color. It is uncanny how colorless it is - once you see a D color diamond you will know it. The scale progresses up in letters, with a little more tint of color in each. Most lay people will find it difficult to see the difference between an E color and an F color - it's pretty subtle. When you hit J color, that's the rough line where we consider it to be a tinted stone. That is, the diamond obviously has a color cast to it to the naked eye. The "average", or "commercial" color that is a good compromise of quality and cost for most people is G to H color. It is also permissible to use mid-grades, so there is such a grade as G-H or E-F, partway in between. There are Master Stone Sets of the diamond colors, so that real graders, like GIA, aren't guessing or being arbitrary. A G color is a G color, and nothing else.
Clarity is an assessment of how many impurities are in the stone. The industry has gotten away from the word, "Flaws" because it is bad PR, and also not really true. We use the word, "Inclusions", which is more accurate and gentle. There are two basic forms of inclusions - foreign objects, often crystals of diamond or other minerals that were trapped when the main crystal grew, and cleavages (often called "Feathers"), which are imperfections in the crystal itself. Diamond will split just like wood, though more perfectly than wood, and if there is a tiny split in the grain, and air or gas gets in the seam, then you see a feather. Inclusions will look like grains or particles - they are never "carbon" - more likely crystals of garnet or peridot, and often small diamond crystals. Cleavages, or feathers look like wispy veils - as though you put a fine silk curtain across. As a standard, all clarity grading is done under 10 power magnification. Most jewelers loupes are 10x, and the gem scopes you see are also 10x. Gem scopes can go to higher powers, usually, and one might search a stone under, say 30x, but if you find something, but then you can't see it under 10x, it doesn't count. It is also only what you can see from the top of the stone. If you see something in the bottom, and then turn the stone over and you can't see it from the top, again, it doesn't count.
The grades of clarity are Fl, IF, VVS, VS, SI, and I. Fl is flawless, which means that the EXPERIENCED observer (all grades presuppose an experienced observer) can find nothing under 10x. The FL grade is rigorous and rare. IF means Internally Flawless, which means the inside is flawless, but there is some scratch or similar on the surface. The other grades have 2 sub-grades, so there is VS1 and VS2 - just a matter of degree. VVS means very, very slightly included, VS is very slightly, SI is slightly included, and I is included. In practical terms, get a 3" by 5" index card and a pencil. If you drop the pencil near the edge of the card, on it's point so it leaves a dot, or maybe twice, then that is VVS1. If you do it 3 or 4 times, or do it near the center, that is VVS2. If you do the same thing with a fine tipped felt tip, that is VS1 and VS2. If you do it with a magic marker, then that is SI1 and SI2. All of this, in a real diamond, is under 10x. If you can see anything with the naked eye, then you have "I" clarity. I1 means you can see it, I3 looks like you took a hot marble and dropped it in cold water. There is a recent grade of SI3, which means that the stone is full of stuff, but you still can't see any of it with the naked eye.
The final C is Cut. Beginning buyers often think that means the shape of the stone, and it does to a small degree. What it really means is related to how light passes through the stone. In the link page on our website is a link to "The Diamond Cut Study", which, once you find the place, is a graphical, animated rendering of the passage of light through a diamond, and how it can vary. Without getting too technical: A gentleman named Tolkowski sat down one day and did some calculations. There is a physical property called "Refractive Index". If one sends a ray of light at the surface of any transparent material, it will pass through it. Change the angle of the light by one degree, and it will still pass through it. Change it again, and again, always by one degree, and there will come one angle, which is different for each material, when the light will not pass through but will reflect off the surface. That angle is represented in the refractive index. Mr. Tolkowski figured the angles of a diamond such that (theoretically) all of the light entering a diamond is reflecting off the surfaces on the inside, and is returned through the top, which is a pretty good trick when you think about it. That model that he calculated is what we know of today as "The Modern Brilliant Cut". There is a test that illustrates this, and it's good to know anyway. Take a round Cubic Zirconia and turn it upside down on some newspaper print. If you look close, you can see the print through the bottom of the stone. If you do the same with a diamond, you will not be able to see the print. This is because the RI of CZ is different, and the light does come through. The light, and the newsprint, in the diamond is being reflected back down to the paper underneath. Note that this only applies to round shaped stones. The angles in fancy shaped stones vary around the perimeter of the stone. Thus the final C - Cut - is about how closely the stone in question follows the ideal of Mr. Tolkowski. There are stones available called "Ideal Cut" that are purposefully cut to as near as possible to the ideal, and are always priced accordingly. I'm not going to delve into the math - table percentages and the like, here. Just so you understand the importance of cut - it is directly responsible for the brilliance of a diamond, and how much light is coming to the observer through the top of the stone. People in the trade refer to the "Make" of a stone, which is the whole package: the proportions, the polish, symmetry, and everything about how the stone was "Made".
So, what does all of this mean? "I'm thoroughly confused, and all I want is a diamond for my girl!!!" If you are buying an engagement ring, I feel the most important thing to understand is what you are buying. Put a diamond ring on your finger, and what are you looking at? You are looking at the color, and the cut. Assuming the stone is not "I" clarity, you're not going to see any inclusions with the ring on your finger, only at 10x. So clarity is about money, and value, but you don't see it on your finger. The most important thing of all, the thing that buyers often don't realize, is the cut. If you'll remember my example way up above about a $5000 stone vs a $3500 stone, most likely the difference will largely be the cut. One stone will be fine looking, and one will be a little flat and lifeless. What color they are doesn't mean much because it's a dead stone. A finely cut ("Made") diamond should flash and sparkle at every angle. You might see prismatic lights on the walls around you when it catches a ray of sunlight. It should have life. When you're buying a stone, you'll find that usually one color grade is comparable to one clarity grade (unless it's flawless). So a G color VS stone might be close in price to an F color SI stone. Up one color grade, down one clarity grade. My suggestion is to go for color whenever possible. The first thing a diamond dealer will do is not pull out the loupe, or look at the numbers - they will look at the stone itself, and assess what it looks like as a whole. That's what you should do, too. Last bits of advice: Look at lots of diamonds, be informed. When we sell a diamond, we WANT the customer to know what they are buying, and why. We want them to be educated - an educated diamond buyer is a happy diamond buyer. Never buy a stone without looking at it under 10x. NEVER. If you go into a store, and they give you any kind of hard time about magnification, just walk out. People want all sorts of things involving diamonds - earring studs are often not-so-high quality because they are way up on the ears. If you are buying an engagement stone, though, you are buying and heirloom, take your time, be informed, get the right stone.