Most people evaluate diamonds using the four Cs - cut, clarity, color and carat weight. These four qualities define a diamond's value, and knowing what they mean will help you when selecting a diamond.

Cut refers to the shape of the diamond, the number of facets, and the quality of the cut. Though diamonds are available in a number of shapes - such as round, pear, heart, oval, marquise, emerald and princess - a well-cut diamond of any shape will reflect light and sparkle with intensity.

"Fire" and "brilliance" are terms that describe the intensity of the color and brightness of the light seen in a diamond. These qualities are achieved by cutting the stone to exacting mathematical proportions so that as much light as possible is reflected out the top of the diamond.

Most natural diamonds contain identifying marks known as inclusions, many of which are invisible to the naked eye. Diamonds having fewer and less noticeable marks are rarer and command higher prices.

A diamond's clarity ranking is determined by the number, size, type and placement of inclusions visible under the scrutiny of a 10x magnifying loupe or microscope. Internally flawless diamonds are very rare and expensive. An inclusion directly under the diamond's table, or top, will reduce its rating more than one in the girdle, or side. Carefully examine the position of inclusions because a crack from the surface to the interior could result in a broken diamond if the stone is hit the wrong way. Michael Anthony Jewelers does not sell diamonds below the "S12" clarity grade.

The following scale, developed by the Gemological Institute of America (GIA) and commonly used in the United States, contains definitions for different clarity grades.

Most diamonds appear colorless but actually have slight tones of yellow or brown. Diamond color is graded on a scale of D (colorless) to Z (heavily tinted), and the closer a diamond is to being colorless, the more valuable it is. Even when a diamond has a visible tint such as K or above, it can still be beautiful if it has good clarity and cut.

The color of a diamond can appear different once it is set. A colorless diamond might look a little yellow when set in yellow gold, while a slightly yellow-tinted diamond might appear whiter in that same yellow setting. Diamonds outside the normal color range are called fancy colored. Graded as Z+, fancy colored diamonds come in a variety of colors like red (the rarest), pink, violet, blue, green, and bright yellow, known as "canary." Stones with good color are rare and can sell for more than white diamonds. Michael Athony Jewlers does not sell diamonds that are below an "I" color.

Carat is the term used to describe the weight of any gemstone, including diamonds. Diamond weights are stated in metric carats or "ct" (versus the karat amount of gold contained in an item). One metric carat is just over seven thousandths (0.007) of an ounce. Since 1913 the international standard has been 1 carat = 200 milligrams, or 1/5 of a gram. In jewelry pieces with more than one diamond, the carats may be described in terms of total carat weight (TW). This number is the combined total weight of all stones in the piece.

Large diamonds are very rare. In fact, 23 tons of diamond ore must be mined to produce a single one-carat, gem-quality diamond. Diamonds come from the mines in crystals, often with eight sides. As much as 60 percent of the original crystal is cut away to create a round brilliant diamond. Stones that are smaller than one carat can be measured a number of ways - in fractions, in decimals, or in points. One carat equals 100 points, so a ¾ carat diamond is the same size as a .75-carat diamond or a 75-point diamond. Expect to pay a premium for stones that are above one-carat weight.

Round brilliant cuts follow exact standards, so you can make a good estimate of the carat weight of the stone based on the stone's diameter. The following chart compares the relative sizes of stones and describes how much a round brilliant diamond of a certain size is likely to weigh. (Note: This method does not work as well for other cuts or shapes, or for colored gemstones, which have a different density from diamonds.)

For all the beauty and complexity of well-cut diamonds, they are the simplest of gemstones in the chemical sense - pure carbon, the same as the graphite in a pencil. Diamonds are formed under intense heat and pressure deep within the earth and are forced to the surface by geological events. They are harder than any other material on earth and can be cut only by other diamonds. Their hardness and other special qualities - such as how they refract light - allow them to be cut into the amazing gems we know today.

Even though diamonds are very durable, they require special care to keep them looking their best. We recommend that you have your diamonds cleaned professionally on a regular basis. You can also use a mild ammonia and water solution with a soft-bristled, non-metallic brush to gently scrub away dirt buildup around the prongs. However, avoid ultrasonic cleaners if your stone has a serious crack or inclusion. The vibrations of ultrasonic cleaners can enlarge such flaws.

When you have your jewelry cleaned, ask the jeweler to check the settings to be sure all stones are secure. If a stone is loose, have it repaired immediately. Also avoid setting diamonds in very soft metals like 24K gold, which bends easily.

Store your diamonds separately from other jewelry. Diamonds can scratch other gemstones, especially pearls, as well as other diamonds.