THE "FOUR C'S" OF DIAMONDS
Fine diamonds are among the most coveted of all gems. Their value, however, differs widely from one diamond to another. Experts evaluate every diamond for rarity and beauty, using four primary guidelines. These are called The Four C's—Cut, Color, Clarity, and Carat Weight.
CUT:
When you think of the cut, you probably think of the shape of the diamond. You are partially correct. While cut does refer to shape, it also refers to the proportions of how the diamond is actually cut.
Diamonds are cut into many different shapes, reflecting not only popular taste but the proportions and quality of the rough diamond. The most popular shapes include Round, Oval, Square, Princess, Emerald, Baquette, and Marquise cuts. Many specialty shapes are also available.
A diamond's overall proportions, as well as the size and placement of its many reflective surfaces or facets, also play a large part in "cut." The consistency and balance of these can greatly affect how the stone captures light and reflects it back to the eye.
COLOR:
With the exception of some fancy colored diamonds, the most valuable diamonds are those with the least color. The color scale for transparent diamonds runs from D-F (colorless), G-J (near colorless), K-L (faint yellow), to Z (light yellow). Completely colorless diamonds are rare.
When diamonds are formed with traces of other minerals, rare and beautiful colors can result. These "fancy" colors range from blue to brilliant yellow to red, brown, pale green, pink, and violet. Because of their rarity, colored diamonds are highly desirable and may be quite valuable.
CLARITY:
A diamond's clarity is measured by the existence, or absence, of visible flaws. Tiny surface blemishes or internal inclusions -- even those seen only under magnification with a jeweler's loupe -- can alter the brilliance of the diamond and, thus, effects its value. Clarity levels begin with Flawless (F & IF) and move down to Very Very Slight (VVS1 & 2), Very Slight (VS1 & 2), Slightly Included (SI1 & 2), and Included (I1, 2 & 3).
FL, IF Diamonds Flawless: No internal or external flaws Internally Flawless: No internal flaws
VVS1, VVS2 Diamonds Very, Very Slightly Included: Very difficult to see inclusions under 10% magnification.
VS1, VS2 Diamonds Very Slightly included: Inclusions are not typically visible to the unaided eye,
SI1, SI2 Diamonds Slightly included: Inclusions are visible under 10× magnification and may be visible to the unaided eye.
I1, I2, I3 Diamonds Included: Inclusions are visible with the unaided eye.
CARAT WEIGHT:
The size of a diamond is measured, not by its dimensions, but by weight. One carat, the traditional unit of measure for diamonds, is equal to approximately 0.2 grams. You may also hear the weight of a diamond referred to in points. A point is equal to 1/100 of a carat; therefore, a 75-point diamond equals 0.75 carat. Diamonds of equal weight may appear slightly different in size, depending on their depth and proportions. Because they are quite rare, larger diamonds of gem quality are much more valuable.
THE 4 C'S OF COLORED GEMSTONES
Where do you begin the journey into the magical world of color? What are the factors that make a gem rare and valuable?
Much like a diamond, the various combinations of a stone's cut, color, clarity, and carat weight, along with availability and accessibility, determine rarity. You will find a brief description of those features here. These explanations are based on the system for gemstone evaluation established by the Gemological Institute of America. For more information on GIA, please visit www.gia.org.
COLOR:
Color is typically the most important value-setting factor for gemstones. All gems have a preferred color or a relatively small range of preferred colors. The more the color varies from this range—lighter or darker, more vivid or less—the less valuable the stone.
Color is composed of three dimensions: hue, tone, and saturation.
Hue refers to the impression of color usually noticed immediately, such as red, yellow or blue.
Tone refers to the degree of lightness or darkness of an object.
Saturation defines the degree of purity of a hue.
CUT:
Cut refers to the shape or design of a stone, arrangement of facets, as well as the precision of the stone's proportions and finish. The cutting process reveals the beauty of a gem.
Gemstones are cut into shapes we are familiar with such as oval, emerald, pear, round, and marquise. In addition, they can be carved or fashioned into almost any design imaginable. Proportions involve the balance and appeal of the basic design. Finish refers to the detail of the workmanship. A well-proportioned cut with a fine finish will show a stone's optical properties to its fullest potential. When all other factors are even (color, clarity, and carat weight), a better-cut gem will be more valuable.
CARAT WEIGHT:
The size of a gemstone is measured, not by its dimensions, but by weight. One carat, the traditional unit of measurement for gemstones, is equal to approximately 0.2 grams. You may also hear the weight of a gemstone referred to in points. A point is equal to 1/100 of a carat; therefore a 75-point gemstone equals 0.75 carat.
Two different gemstones may have the same dimensions but different weights. This is due to the specific gravity or density of the gem mineral. This difference can help gemologists identify a gemstone.
Up to a certain point, the larger a stone is, the more rare it is and the higher the price it will command. For stones that commonly occur in larger sizes, the value may decrease if the gem reaches a size that makes it impractical for jewelry use.
Source: Gemological Institute of America
CLARITY:
A gemstone's clarity grade is directly related to its rarity. Clarity refers to a gemstone’s relative freedom from clarity characteristics. Clarity characteristics include inclusions, which lie within the stone, or blemishes, which lie on the surface of a gem. The fewer clarity characteristics, the more rare the gemstone.
Each variety of gemstone has its own clarity standards. For example, Tanzanite is virtually inclusion-free, while Emerald almost always contains clarity characteristics. For this reason, Gemological Institute of America's grading system divides transparent colored gemstones into three clarity types. This allows gems to be more evenly evaluated as it takes into account the individual nature of each gemstone. Each type is further divided into five grading descriptions.
CLARITY TYPES:
Type I gems are often virtually free of clarity characteristics. The stones most commonly seen in the market include:
Aquamarine
Green Tourmaline
Morganite
Smoky Quartz
Green Tourmaline
Tanzanite
Topaz – Blue
Zircon – Blue
Type II gems normally contain clarity characteristics. The stones most commonly seen in the market include:
Alexandrite
Garnet
Zircon – Green
Amethyst
Iolite
Sapphire – all colors
Zircon – Orange
Ametrine
Peridot
Spinel - all colors
Zircon - Red
Citrine
Ruby
Tourmaline
Zircon - Yellow
Type III gems almost always contain clarity characteristics. These include:
Emerald
Tourmaline – Watermelon
CLARITY GRADES:
Type I:
Usually eye-clean with no clarity characteristics visible to the unaided eye.
Type II:
Typically shows some eye-visible clarity characteristics that do not detract from the overall beauty of the gem.
Type III:
Almost always contain eye-visible clarity characteristics.