Summary: Buying antique or estate jewelry? Remember the four Cs: cut, color, clarity and carat weight and be aware of two more: cost & credibility, to be sure you're getting an antique, not just used jewelry.

When buying antique or estate jewelry, there's more to keep in mind than just the four Cs (cut, color, clarity and carat weight ). You've got to know whether you're purchasing an actual antique or simply an estate piece. So consider two more Cs: cost and credibility.

Cut: The way a diamond is cut affects its appearance, durability and worth. Diamonds are cut into shapes that show off their individual brilliance and clarity. The most popular cut for diamonds is round (brilliant). However, other popular styles are the baguette, marquise, oval, pear and square (princess) cut.

Color: Diamonds range in color grades starting from D through to Z. Many diamonds appear to be white (or colorless), but they may contain traces of other elements that impart slight yellowish or brownish tints. Color variants among diamonds in the D-F range are often very slight. Stones as far along the scale as G are still largely clear; but the further you get from a D rating, the deeper the color concentration.

Some diamonds occur naturally in what are termed "fancy" colors: blues, bright yellows, greens, pinks and even vivid reds. These diamonds are extremely rare and are considered highly valuable.

Clarity: Clarity refers to the size and amount of inclusions in a diamond. Most are merely traces of carbon that didn't crystallize during formation, undetectable by the naked eye. The average consumer would need a microscope (and a considerable period of scrutiny) to see them.

The greater the number of inclusions in a diamond, the higher the interference with the gem's light dispersion; this diminishes the stone's brilliance. Large or plentiful inclusions also decrease a diamond's value. And the fewer (or smaller) the inclusions, the more valuable the gem.

Diamonds are rated according to their clarity under 10x magnification with a jeweler's loupe. Diamonds rated FL are completely flawless; these are extremely rare and costly. Those rated IF contain only external flaws, which may be removed by further polishing. Diamonds rated VVS1 and VVS2 have very, very slight inclusions. VS1 and VS2-rated diamonds have very slight inclusions. SI1 and SI2-rated stones have slight inclusions; and I1- I2- and I3-rated diamonds have large, visible blemishes, visible to the naked eye.

Carat Weight: Diamonds are measured in carats; this measurement doesn't refer to their size, shape or diameter - just their weight. Because one carat may be divided into units of 100 points, a 3/4-carat diamond is described as being 75 points or 0.75 carat. The larger the diamond, the more expensive its per-carat cost; expect to pay more for a one-carat diamond than for two half-carat diamonds of similar cut and clarity.

Cost & Credibility: The better the quality of your diamond, the more it is worth. But don't assume you're getting a valuable diamond because it's pricy. This is where credibility is crucial. Are you buying this diamond from a reputable dealer? Are you really getting what the dealer says you're getting? Is this ring an "antique" or is it really just "estate" (a fancy term for pre-owned) jewelry? The best way to know for sure is by knowing your jeweler. To get the best quality for your dollar - from a trustworthy dealer with years of experience - visit Estate Diamond Jewelry. All they do is estate and antique jewelry.