In its most common form, carbon looks like so much black dust. In rare cases, heat and pressure transform it into a diamond. Unusual and beautiful even as uncut stones, diamonds require skilled cutting to reveal their true brilliance.
Although each diamond is unique, appraisers and jewelers grade their quality to facilitate standardized pricing. Diamond quality relations on four characteristics: cut, color, clarity and carat weight. These "four C's" determine a diamond's value, but not necessarily its desirability.
When jewelers refer to a diamond's cut, they mean not the shape, but the stone's proportions. The facets of a diamond are positioned to reflect light through the table facet, the large flat facet atop the gem. A skilled lapidary cuts the facets at the proper depth to maximize the light that reaches the viewer through the table facet while minimizing light lost to the underside of the diamond. A cut that's too deep lets rays of light leave the diamond's sides, while an overly shallow cut allows light to leak through the pointed bottom of the stone.
Cut is one of the most difficult aspects of diamond quality to discern for anyone but experienced jewelers. Look for ideal, premium or good cuts for a higher quality stone. Fair and poor cuts cost less, but have noticeably less brilliance and fire than a well-cut gem.
Most diamonds have a color cast to them. Those that do not are so rare that they command the highest prices. Jewelers rate diamonds on a scale from D to Z in color, with D being completely colorless gems and Z being markedly tinged, usually with brown or tan. Any diamond in the G to J range has so little color that it's imperceptible to the untrained eye, while diamonds ranked K through M have only a faint warm hue. These diamonds represent an excellent value for jewelry. If they're set in yellow gold, their champagne tint is invisible.
A clear diamond transmits more light than a cloudy or flawed one. Types of flaws vary, and some are more disfiguring than others. Simply looking at a diamond with unaided eyes will reveal larger flaws; these diamonds are rated imperfect and designated I1, I2 or I3. Smaller inclusions that only appear under a jeweler's loupe at 10X magnification are considered small; these diamonds are rated SI1 or SI2. Most jewelry from chain stores falls into this category. Diamonds with very small inclusions, or VS1 and VS2 stones, fetch higher prices. If a gem bears the VVS1 or VVS2 designation, it's almost perfect and will bring a higher price. Flawless stones are labeled FL or IF and are extremely rare.
A larger diamond costs more than a smaller one not only because there's more diamond, but because of its relative rarity. Large diamond crystals form more infinitely than smaller ones, so higher carat weights command higher prices.
Tips for Choosing Quality Diamonds
– Only experienced appraisers and jewelers can reliably rate a diamond's quality, so seek their expert advice when buying diamonds.
– Rank the "C's" in order of importance. Some people like larger diamonds regardless of their color or clarity, while others prefer a small, but brilliant stone. Deciding which characteristic is least important helps keep costs lower.
– If possible, view the stone outside of its setting.
– Borrow the jeweler's loupe and examine the stone under magnification.
– Black freckles of carbon in the diamond affect its fire less than cloudy white veils. If given a choice between two other equivalent diamonds, choose the one with freckles over the veiled stone.
– The eye test is often the best indicator of quality. A high-quality diamond looks like exactly what it is: a sparkling work of art.