Diamonds, Gemstones and Pearls

Below are are tips to help you understand Diamonds, gemstones, and Pearls in general and, more specifically, what Hamilton Hill offers and recommends. Since we are passionate about such things, we look forward to explaining more to you in person and to answering your questions.

Carat: Unit of Measure for Diamond and Gemstone Weight
Diamonds and gemstones are weighed in carats (derived from the word carob, as in carob seed). A carat translates to 200 mg, 0.2 grams, or 0.007055 ounces. For stones weighing less than a carat, the unit of measure is “points,” with one carat consisting of 100 points. (The purity of gold, strangely enough, is referred to with the word karat. Same sound, quite a different meaning.)

Millimeter: How stones and pearls are measured for length, width, depth 
Round stones are measured for their diameter and depth in millimeters. Non-round stones have a millimeter length, width, and depth. Individual pearls are often referred to with a millimeter range, such as 6.0–6.5mm. 

Diamond and stone cutters create facets or smooth surfaces/planes that make up the faceting pattern. Common faceting patterns include brilliants, step cuts, and rose cuts. Cabochon cuts are smooth and domed, generally having no facets at all. Fantasy or specialty cuts may have hundreds of facets or ingeniously placed facets designed to create optical illusions. Occasionally, pearls are faceted, too.

Diamond and gemstones can be cut into an endless number of shapes with the most common being round. Pearls form as spherical, off-round, baroque, and more.

Cut can refer to a stone’s shape or faceting pattern, but here we use it to refer to proportion, symmetry, and polish, or the precision achieved in the cutting, faceting, polishing process. A precisely cut and highly symmetrical Diamond shows more fire and brilliance, i.e., more effectively processes light, than those less precisely cut or symmetrical. Modern brilliant-cut Diamonds are valued for their “light effects” and even colored gemstones such as Sapphires are often “diamond cut” to increase sparkle and make setting easier.

Diamonds are most commonly graded and valued for their lack of body color, though when they are “fancy colored” (e.g., “canary” yellow, pink, red, blue), they are generally valued for their depth of color. Grading scales differ for “white” Diamonds and “fancy colored” Diamonds, with white Diamonds having letter grades such as D, I, and M and fancy colored Diamonds having terms such as light, intense, and vivid.

When choosing a white Diamond, most Hamilton Hill clients choose a color grade of D through J. That variation affects the price, and at some points along the color scale, the look. We will help you learn to see the difference — often so faint as to be nearly imperceptible, especially when set — and help you make an appropriate selection based on your wants and needs.

Gemstones are “color” graded and valued using the combination of hue (shade of color), tone (intensity of color), and saturation (purity of color). Some colors are more highly valued in the world at large, but beauty is in the eye of the beholder making color choice one of personal preference.

Diamonds are graded very strictly for their internal clarity which includes the number, size, location, and relief of inclusions (commonly referred to as flaws). Unless the inclusions causes durability issues or undermine the diamond’s beauty, they can be considered clarity characteristics. They are there as proof of their natural origin, created by pressure and heat deep within the earth’s core.

Laboratory Reports
Many Diamonds 0.50 carat and above sold by Hamilton Hill will be accompanied by reports by outside diamond grading labs such as GIA (Gemological Institute of America) or AGS (American Gem Society). Sarah Hill and Shelly Thompson of Hamilton Hill both have GIA diamond grading training, and though Hamilton Hill does not issue its own lab reports, we can informally grade and of course verify reports. Hamilton Hill can also submit Diamonds to be graded by these outside labs.