When dealing with diamonds, everyone tells you to watch out for the "Four Cs": Cut, Color, Clarity, and Carat weight. One has no quantitative scale at all but is, rather, simply a buyer's preference. Two of them have handy scales — determined by the Gemological Institute of America (GIA) — that you can refer to, quickly, and understand. The fourth, however, is so simple to understand that I almost don't want to insult your intelligence by discussing it. (But I will.)
CUT - Let's get the hardest one out of the way, first, shall we?
MOST diamonds available are Round Brilliant Cut. This cut is fairly standard — its shape and proportions are nearly consistent, across the board. A diamond of this cut is shaped in such a way as to refract all light hitting the gem to be reflected back out through the top of the stone. (It's sparkly!) See this image for an illustration of light coming through the top of a diamond.
If a Round Cut Diamond doesn't follow this specific, mathematical procedure, you'll end up with a gem that looks like a diamond, but doesn't have that certain "sparkle" that a Diamond should have. To ensure you get a quality Round Cut, the gem should come with an American Gem Society Diamond Grading Certificate.
Even though a Round Cut is the most common, there are other cuts. A different cut doesn't mean the gem won't impress the lady come gifting time. Among the other, common cuts are the Baguette Cut and Princess Cut. Baguette Diamonds are cut to show off the rock's luster, whiteness, and clarity but it doesn't sparkle as much (it has less "fire".) Princess Cuts, however, accentuate the fire and brilliance, but are not as lustrous.
COLOR - Clear diamonds, or Type I, have Nitrogen as their main impurity. Now, calm down, I hear you saying, "I don't want ANY impurities in MY diamonds!" Well, tough. If you want a clear diamond, you're going to have to suffer. Type I's are scaled, by letter, from LEAST impure to MOST impure.
According to the GIA color grading scale (the most common scale), Colorless stones are graded from D to F, Near Colorless from G to J, Faint Yellows are graded K to M, Very Light Yellows are N to R, and light Yellows are S to Z.
So, a grade D is "OOOOH! Sparkly!" and a grade Z is "Um... did someone pee on your diamond?
Gems with little or no Nitrogen are Type II diamonds. These are the diamonds that can be colored Pink, Red, or Blue. These are a more rare type of diamond (only 1.8% of all diamonds mined are in this range.) Thus, they are more expensive. There is no scale for grading this sub-set of rare diamonds.
CLARITY - Clarity is judged based on inclusions and blemishes.
Inclusions is a term that refers to anything within the diamond that affects its luster or brilliance. Inclusions are things like cavities, clouds, or other internal flaws.
Blemishes are anything externally that affects the sparkle of the gem. Blemishes include polish lines, scratches, nicks, pits, and chips.
Once again, the GIA jumps in with a handy scale, though this one is not as direct, as it balances and judges both internal and external flaws before deciding on it's grade. The grades, from best to least-best are: Flawless gems are given an FL grade, Internally Flawless are IF, Very Very Slightly Included are VVS1 and VVS2, Very Slightly Included are VS1 and VS2, Slightly Included are SI1 and SI2, and Included are I1, I2, and I3.
Except for the I1, I2, and I3 categories, all of the other grades will show flaws, to the trained eye, under a 10x magnification. However, the Included category contain diamonds with flaws that are easy to see with the naked eye.
So, a FL diamond is "E-Gads, my eyes can't handle the beauty!" whereas I3 diamonds are, "I think you need to clean your diamond."
CARAT WEIGHT - This is the easiest grade to understand. In short, the higher the carat weight, the bigger the diamond. Keep in mind, of course, that the bigger the diamond, the bigger the price. Interestingly, though, since bigger diamonds are harder to find than smaller ones, it's not a direct size-to-price scale. As the carat weight goes up, the price jumps, considerably. So, a 1-carat diamond will cost more than twice the price of a 1/2-carat diamond.
Other nomenclature you might run into when buying the "big sparkly":
K - Carat This relates to the measure of the purity of Gold or Platinum and is different from Carat Weight. You'll come across this abreviation while buying diamond rings or earrings. For instance: "Diamond 18K White Gold Ring" - that 14K is not refering to the weight of the diamond, but the type of gold used in the ring itself. Pure Gold (and, thus, the most sought-after and expensive) is graded as 24 carat (K) and the scale slides down, from there. Therefore, 18K Gold is only 75% Gold and 25% impurities by mass.
TCW - Total Carat Weight Many merchants will list a TCW number on items which have more than one diamond or gem. This label is especially tricky when purchasing earrings. Why? Well, if a merchant says that a pair of diamond earrings has "1/2 TCW diamonds". What they are really saying is that the earrings only have 1/4-carat diamonds on each of the posts. But, of course, merchants know that you'd rather have 1/2-carat diamonds, so they add the total weight up, and advertise it like that.
CZ - CZ stands for Cubic Zirconium. That means it's not a diamond.
Well, I hope all that helps. Now you're ready to spend a month's worth of salary on your lady. You know she's worth it. It's time to see the latest jewelry deals we've found on dealnews.
Jeff Somogyi is the dealnews Senior Staffwriter. His inclusions are so severe that he falls off the Clarity Scale altogether.