How to buy a diamond
Cut gives the diamond its brilliance. Of the four C's, Cut is the only contribution made by man transforming the rough diamond crystal into a faceted, polished gem.
After thousands years of experiments, using precise mathematical formulas, the cutter transforms nowadays a diamond in the rough into a sparkling jewel that reflects and refracts light. When the term "cut" is first introduced, most people think of the diamond's shape.
However, "cut" refers to the diamond's proportions and finish, while shape is the final result after cutting process have been finalized. The cutter's primary objectives are to produce the largest size diamond from the given rough stone and achieve the greatest optical beauty.
There are many different types of diamond cuts. The most common is the round brilliant, which has 57 facets after Marcel Tolkowsky's widely accepted formulas. There are also several very common variations on the round brilliant - the oval, the marquise, some cushion cuts, and the pear. All of which, in standard form, have 57 facets. Other very common diamond cuts are the heart, the step, and the princess. The sky is the limit as far as diamond cuts go. It seems there are 255 registered diamond cuts. When a diamond is cut to proper proportions and is finished well, light refracts into the diamond, is reflected from one facet to another and then returns through the top of the gem resulting in a display of brilliance (white light), dispersion (rainbow-colored light) and scintillation (sparkling when the diamond moves), and luster (bright reflections from the surface). Proper cutting is the key to a diamond's beauty and value, but again more proper cutting done, more expensive the diamond is, finally.
To understand the sub-categories for well-cut diamonds, think of a pyramid with "Ideal" at the top. This narrow range is reserved for the most brilliant, rare and valuable diamonds. The "Excellent" range includes beautiful diamonds that return almost as much light. "Very Good" represents the balance between precise proportions and price considerations.
In many cases, the visual differences may be indiscernible to the naked eye.
Each Diamond part has a function:
The Crown gives balance, brilliance, dispersion, and scintillation.
Girdle provides a setting edge for the gem.
The Pavilion reflects light back up through the crown.
The Culet prevent chipping at the tip.
Ideal & Fine Cut
When a diamond is cut to proper proportions, light is reflected from one facet to another and then dispersed through the top of the stone, back to the eye.
When the cut of a diamond is too deep, some light escapes through the opposite side of the pavilion. The Diamond appears dark face-up.
When the cut of a diamond is too shallow, light escapes through the pavilion before it can be reflected. Diamond appears "washed-out", or "watery" face-up. The Girdle may reflect into table facet.
Finally we can come to diamonds shapes. Find yours favorite diamond shapes among the most popular and flattering shapes shown here. Diamonds are cut in many shapes, as mentioned in the above, either modern or traditional.
The shape of a diamond refers to its basic form: round, oval, pear-shaped etc. Shape is often confused with the cut. Shape is simply a matter of personal preference. The most common and preferred in general is the round-brilliant shape, the other shapes being considered "fancy shapes".
For a ring, you might choose also a marquise or oval shape because it makes your finger appear longer. Pear-shaped diamonds look best on smaller fingers. Traditionally, stud earrings are in the classic round or princess shape. Emerald shape became very common recently, mainly in multiple combinations.
Like fashion, the shape of a diamond can express your personality or your individuality.