Before you begin your search for a diamond of your own, you should know as much about how diamonds are graded. That’s where this guide comes in. When you’re done with your Diamond Education here, you’ll be able understand what the jewelers are talking about.
The first things you should learn are the 4 C’s. That’s Carat, Color, Clarity and Cut. Once you know this stuff, you will be able to evaluate diamonds on your own.
A carat is a measure of weight used to weigh diamonds and other gem stones. The word “carat” is a term taken from ancient history, the carob seed. Carob seeds were used to balance scales because of their uniform shape and weight. Even with today’s measurement devices, these seeds weight is uniform to three one-thousandths of each other.
The process that creates diamonds happens very rarely and the natural materials required for this to happen are found only in small amounts. That means that larger diamonds are much more rarer than smaller diamonds causing the price of larger diamonds to rise exponentially according to its size.
Note: Do not confuse “carat weight” with “karat,” the term used to determine the purity of gold.
Diamond color is determined by the amount of color in the stone. The less color there is in a diamond, the better. Color in a diamond will diminish the fire of the diamond.
The highest color grade which is extremely rare. The diamond is perfectly white.
Colorless. Only minute traces of color can be seen by an expert gemologist. Also very rare.
Colorless. Slight color can be seen by an expert gemologist, but is still considered colorless.
This is a high quality diamond.
G - H
Nearly colorless. The color can be noticeable when compared to a diamond with a better grade. These diamonds are an excellent value.
I - J
Nearly Colorless. Color slightly detectable. Still and excellent value.
K - M
Yellowish or Brownish Color. Color is detectable with the naked eye.
N - Z
Yellowish or Brownish Color. Color is detectable from a mile away.
Note that fancy colored diamonds such as yellow fancy and blue fancy colored diamonds do not follow this chart.
There are many methods of enhancing diamond colors. Some are to whiten white diamonds
and others are to enhance the color with diamonds with not-so-good color. At DiamondZul.com, we use color enhancement to create fancy colored diamonds only. We do not use any methods to raise the grades of white diamonds. Such as enhancing a “G” color diamond to “E”. The different methods we use to enhance the color in our diamonds are HPHT, Irradiation and Surface Enhancement. All our items are clearly labeled as Enhanced on our item description.
HPHT is a process developed by General Electric in 1999 to color treat diamonds. This process puts over 60 kbar (nearly 1,000,000 psi) of pressure on the diamond at around 1400°C (2550°F). Diamonds treated with HPHT can transform into many colors including to pinks and blues. HPHT can also be used to create white diamonds, however
will only use this process to create fancy colored diamonds. This treatment is permanent and will not be affected by cleaning or heat from setting repairs.
Irradiation treatment involves exposing the diamond to electromagnetic rays to release electrons from their normal location to a more desirable location changing its color. Neutron bombardment and electron bombardment are the two main irradiation methods practiced today. Diamonds treated by irradiation produce many brilliant colors such as green, yellow, blue and reds. This color treatment is permanent and will not be affected during cleaning processes. However, blue or green enhanced colors could change to a yellowish color if high heat, 300°C (572°F) or more, is used during setting repairs.
Surface Enhanced diamonds are chemically treated to change the color of a diamond to Brilliant colors. This is done by coating the diamond surface with a metal halide. A similar technique used to coat some camera lenses that create the blue reflection. This method can produce vibrant pinks and cognac reds. Care should be taken with surface enhanced diamonds. The coating can wear out during heavy cleaning or heat from setting repairs.
Heat Treatment or 'annealing' is done using a combination of chemicals (beryllium, borax, lead, tantalum) and heat to change the diamond's color. Heating or "cooking" the diamond is done at temperatures ranging from 450°C (842°F) to 1850°C (3362°F) for 2 to 12 hours or more. We only use this process to create our black opaque diamonds. To check if a diamond has been heat-treated, one way is to look for the presence of small fractures within the stone that appear around natural mineral inclusions. This treatment is permanent and will not be affected by cleaning or heat from setting repairs.
fluoresces (glows) blue or yellow under a UV lamp. A diamond with strong or very strong fluorescence can give it a slight hazy or oily look. Some people admire this effect while some avoid it. In diamonds with a low color rating, a high fluorescence might be desirable since it makes the diamond appear whiter. The high fluorescence will add to the value of the diamond. The fluorescence scale rates from none to very strong.
Flawless. No flaws detectable even under 10x magnification! Extremely Rare!
Internally Flawless. No internal flaws, but some surface flaws. Very rare!
Very, Very Slightly included. The inclusions are hard to see in these diamonds.
Very Slightly included. Minute inclusions are difficult to see under 10x magnification.
Slightly Included. Minute inclusions are easier to see with 10x magnification.
Slightly Included-3. SI-3 is a rating that was devised by a some gemological labs to fill a gap between SI-2 and I1. Because of this, not all gemological labs recognize the SI-3 rating such as GIA.
Included. Inclusions are visible with the naked eye.
Opaque clarity diamonds (including our black and fancy color diamonds) can not be seen through or light can not pass through. All opaque clarity diamonds are graded from A to AAAAA by their qualities listed below with AAAAA being the best quality.
Inclusion & Chip-fair-Looks Okay
Close Visible Inclusion & Chip-Good-Looks Good
Very Close Visible Inclusion & No Chip-Very Good-Looks Fine
Clean Silky Surface with Good Make-Best-Looks Great
Clean Silky Surface with Perfect Make-Very Best-Looks Excellent
The cut of a diamond determines its brilliance. There is no single measurement for determining the cut of a diamond. The cut is however a collection of the measurements and observations of a diamond that shows its light performance, dimensions and characteristics. If a diamond has perfect color and clarity, a diamond with a poor cut will have low brilliance. The width and depth of a diamond can have an effect on how light refracts within the diamond.
Too shallow: Light is lost through the bottom giving the diamond a poor brilliance.
Too deep: Light is lost through the sides causing the diamond to appear dark and dull.