While there's a lot we could tell you about buying jewelry in general, this article is going to focus on buying diamonds. Why diamonds? Because diamonds are typically a major investment — the kind of thing you don't want to mess up.
This is what you should understand about diamonds before you go shopping for one.
The 4 Cs: Color, Cut, Clarity, and Carat.
This is one of the things you really have to understand when you're out shopping, because if you don't you're bound to get run over by salespeople who are anxious to close a sale.
The best diamonds are colorless. Fancy colored diamonds — the blues, bright yellows, and pinks — are a separate (and much more expensive) category, so we won't discuss them here.
Diamond color is graded by professionals certified by various gem certification organizations (The GIA and IGI are two that you'll hear mentioned frequently) on a scale that goes from D to Z. Grading is done by eye with the stone loose on a bright white background. This is how you should look at the diamond, even if it's set: on a white piece of paper.
Grades D-F are considered colorless.
Grades G-J are considered near-colorless.
Grades K-M are called faint yellow.
Grades N-R are very light yellow.
Grades S-Z are light yellow.
Most stones in the D-G range are going to look almost identical to an untrained eye. At around H, you may start to see what professionals call "warmth" in the stone: you'll see a very slight tint. After H, that tint becomes much more pronounced. The yellows here aren't exactly a desirable shade: the diamonds often just look dirty (see above photo).
For a white diamond, you'll probably want to stay in the D-I range. An H or an I color diamond won't look too different from a D, but it could be a lot less expensive.
FL — IF: Flawless — Internally Flawless. The rarest stones have no inclusions or blemishes visible to a trained eye with 10x magnification. These are exceptionally expensive.
VVS1 — VVS2: Very, Very Slightly Included. Inclusions that are very difficult to see by a trained grader under magnification.
VS1 — VS2: Very Slightly Included. Inclusions difficult to see under magnification, minor but visible when magnified.
SI1 - SI2: Inclusions visible under 10x magnification.
I1- 13: Included. Usually visible to the naked eye. Diamond appearance affected. In jewelry sales, these stones have a pretty awful nickname: frozen spit.
A VS2 diamond or higher will not have inclusions you can see unless you plan on looking at your diamond with a microscope or jeweler's loupe. The lower grades may be cheaper, but the inclusions may not make for the prettiest stone.
Much of that, however, is dependent on the next C...
What cut boils down to is the way light enters and exits a diamond.
In a well-cut diamond, light enters the top (the "crown" and the "table") and exits the top, like it's absorbing light and spitting it back out in fireworks. In diamonds that are cut too shallow or too deep, the light bleeds out the bottom and sides of the diamond, making it look smaller, darker, and altogether lifeless.
While there are ideal mathematical proportions that describe the angles and percentages needed to make an ideal cut diamond, what you're interested in is the grading certification on the cut: look for Ideal, Excellent, and Very Good. More so than that, let your eyes be the judge. Does the diamond sparkle more or less than the others in the case? Does it look dark when you look down into it?
The diamond pictured above is the Tiffany Diamond It's a cushion-cut, fancy yellow stone weighing 128.54 carats.
Carat weight may be the most widely misunderstood component of diamond buying. Carat is a unit of weight measurement. One carat is equal to one-fifth of a gram (.20g).
What carat does not determine is fire or scintillation. It only determines size and weight. Size and weight do, however, play a role in the fifth "C" of diamond-buying... Cost.
This is important for a couple of a reasons. A man (or woman) who goes out with a budget could very easily come home with the biggest possible diamond for the price. However, if you're just buying for carats, you're going to get a much less attractive stone than if you had bought the best cut, color, and clarity in your price range. A small, well-cut diamond with very good color and clarity will always look better than a larger stone with mediocre color, cut, and clarity.
In other words, bigger is not always better.
By all means, get the largest stone you can afford, but make sure it's also the clearest, best cut, and most colorless stone you can afford. Balance is key.