Diamonds are very valuable, so value needs to be precisely measured. Very slight differences in grade or weight can make big differences in price. Most often, the relative rarity of various characteristics sets value, although expert opinions on beauty and consumer buying patterns can also play a part.
The 4C’s: Carat Weight, Color, Clarity, and Cut.
Thus carat weight is measured to the nearest one-thousandth of a metric carat, rounded to the one-hundredth of a carat, or point. Loose diamonds are weighed directly; mounted weights can be estimated fairly accurately. Most diamonds sold in jewelry range between five points and a carat. Value increases with weight, same as price per carat, because larger stones are rarer. Each rough diamond brings certain characteristics to the cutter. The degree of chemical purity can affect color and clarity; environmental stresses influence external crystal shape and regularity of crystal structure, which in turn determines some clarity characteristics. Given this individual “personality”, cutters try to get the best from each piece of rough diamond. They cannot change the basic features that nature established.
Most diamonds fall in a normal color range from near colorless to slightly yellow, brown, and gray. Actually, diamonds come in all colors, and can be artificially treated to add color; those with distinct attractive natural tints are called fancy colors. How much of the rough’s original color you see depends on size, cut, and mounting. The color of the metal can mask or enhance color. It is easy to explain that the top fancy colors and colorless stones are more valuable because they are rarer. But with the near-colorless end of the normal range, customers often cannot understand why subtle gradations in color, which seem invisible, produce such large price differences. You can use this to sell them a bigger stone for their money or, if they care about quality, explain the significance of this minute distinction.
Natural color in diamonds is caused by impurities and/or crystal distortions and/or natural radiation. The four diamonds types:
Type Ia 98 % of all diamonds; color caused by nitrogen (N3) impurity indicated by 415nm “cape” line in spectroscope.
Type Ib 1.0 % of all diamonds, color caused by single nitrogen atom impurities, cause of the vivid “canary” fancy yellow color.
Type I Ia very rare 99.99 % pure carbon (purest of all diamonds) typically “D” color- colorless! (Cullinan and premier rose)
Type I Ib very rare color caused by boron impurities causes blue color (hope and eugine blue) often causes electrical conductivity treated blue color diamonds do not conduct electricity.
Crystal Distortion: causes Browns, Pinks, and Purplish Reds.
Natural Radiation: changes the selective absorption by creating color centers causes Greens (usually only shallow penetration).
Depends on the presence or absence of surface blemishes or internal inclusions, and ranges from flawless (no characteristics visible under 10x) to imperfect (eye-visible, durability-threatening inclusions). Most stones you will see lie in between. Inclusions are useful to scientists, cutters, and gemologists in separating natural stones from simulants, and as identifying characteristics. They are easy to show to customers under the microscope.
This includes style and make, is the human contribution to beauty. The cutter tries to bring out the best combination of a stone’s inherent characteristics (although weight retention is a factor, too). Normal facet arrangements are brilliant (radiating from the center), step (concentric rows), or mixed. There are many possible shapes; the most common are round, and the fancy shapes, especially square (emerald), oval, marquise, pear, and heart. Proportions are the keys to beauty; finish details are less important.
GIA Diamond Clarity Grades
No Blemishes or Inclusions. Extra facets not visible face-up; naturals confined to and neither thicken the girdle; and internal graining which is not reflective, and which does not affect transparency.
• IF: Internally Flawless.
o No Inclusions and only insignificant blemishes.
• VVS1 and VVS2: Very, Very Slightly Included.
o Minute Inclusions that is difficult to see.
• VS1 and VS2: Very Slightly Included.
o Minor Inclusions ranging from difficult to somewhat easy to see.
• SI1 and SI2: Slightly Included.
o Noticeable Inclusions that are easy (SI1) or very easy to see (SI2).
• I1, I2 and I3: Imperfect.
o Obvious Inclusions that are often easily eye-visible face up, in I3, they may threaten durability.
To determine the overall impact clarity characteristics have on a stone’s appearance and grade, we have to consider five factors: Size, Number, Position, Nature, Color and relief.