The unit of weight measurement for gemstones is called carat. The word is derived from 'carob', from ancient Egyptian times when the carob bean was used as the unit of measurement because of its consistent weight. Do not confuse carat with karat, which refers to the purity of gold.

The following color grades are used by the Gemological Institute of America and are accepted as the industry standard. The purest (entirely colorless) stone is given the color grade of D, and there are extremely slight gradations of increasing color down the alphabet, all the way to Z. Colors more saturated than Z are considered ' fancy'. Diamonds can come in nearly any color.

D, E, F: colorless

G, H, I, J: near colorless

K, L, M: faint yellow or brown

N-Z: very light to light yellow or brown

Fancy: yellow, pink, red, blue, orange, green, gray, black (all colors possible)

F (Flawless): totally free of inclusions (imperfections), both inside and on the surface.

IF (Internally Flawless): has minor surface blemishes, but is otherwise free of inclusions.

VVS1-VVS2: Very very slight inclusions, barely visible to a trained eye using a 10x loupe.

VS1-VS2: Very slight inclusions, visible under a 10x loupe.

SI1-SI2: Slight inclusions, easily recognizable under a 10x loupe. 

I1-I3: Moderate to heavy inclusions, often visible to the naked eye.

The cut of a stone comprises two distinct areas: shape and faceting. Shape is very simply the overall geometric description of how the stone is cut - with the most popular shapes for diamonds being Round, Emerald, Oval, Marquise, Princess or Square, Radiant, Pear and Heart. But there are many variations in cutting styles, and they have changed over the years. A diamond can be cut into almost any shape.

The faceting of a stone is more complicated. It entails cutting the diamond in such a way as to reveal its inner beauty and potential for both dispersing spectral colors and reflecting light back at the viewer. For round stones, there are several different theories for what makes an 'ideal' cut. The GIA now includes a cut grade for round brilliant diamonds, which can be graded excellent, very good, good, fair or poor.

Stones that are not round are considered to have fancy shapes. For these stones there is even less agreement in the industry as to what proportions make an ideal cut. But there are general guidelines used by experienced cutters and industry experts to reveal and maximize the beauty and value of a stone. In the end, the precise measurements and angles don't matter as much as the visual appearance of the stone, as well as your own personal preference.

Cost is an attribute of a stone just like the other four "C"s. Diamond prices are determined by their carat weight, color, clarity and cut, as well as some other attributes. There are always stories of amazing deals that can tempt you to ignore your better judgment. The fact is that you should expect to pay a fair price for your stone. That great deal usually exists because of some small detail that makes the stone worth just about what you paid...and often less. You could pay $2,000 for a 1 carat diamond and have overpaid, or you could pay $10,000 and have gotten a remarkable bargain. If you tell me what you're looking for, I can always recommend the perfect stone to help you maximize value within your budget. I have an excellent understanding of what affects the value of a diamond and will pass on my knowledge to you so that you feel comfortable with your purchase.

For more extensive information about diamonds see the following links. The GIA link brings up the home page of the Gemological Institute of America. The EGL link brings up a consumers guide page for diamonds within the European Gemological Laboratory site.