The cut of the diamond is the arrangement of its facets, its finish and proportions. The cut of a diamond affects how it reflects light from facet to facet and is what makes a diamond sparkle brilliantly.
Crown: The area of a stone above the girdle
Pavilion: The area of the stone below the girdle to its tip.
Girdle: The area where the crown (top) and the pavilion (bottom) of a stone meet. This is the area where the setting of the band holds the stone.
Table: The flat top of a tone. It is also sometimes called the face.
Culet: The small facet on the bottom of a stone, it may help prevent chipping. Not every stone will have a culet.
In an ideal cut, the light coming in through the table should reflect off the facets and back out through the top. This is what makes an ideal cut diamond look so brilliant and fiery. A diamond that is cut too deep or too shallow will lose light through the side or bottom and will look less brilliant.
The mathematics that make up the ideal cut are complex. In 1919, a man named Marcel Tolkowsky calculated the proportions that go into the ideally cut diamond as part of his Ph.D. dissertation.
However, today, diamonds are designed and cut differently than they were in 1919. This means that the proportions and angles involved in an ideal cut are different. I won’t get into a discussion of optics and geometry here, since this is really a topic for gem cutters.
In general you should look at two things, depth percentage and table percentage.
Depth percentage is the depth of the stone (as measured from the table to the culet) as a percentage of the width of the stone. For a round cut diamond, the depth percentage should range from 58%-64%.
Table percentage is the width of the table as a percentage of the total width of the stone. For a round cut diamond, this should be range from 53%-64%.
The bottom line is, when assessing the diamond’s cut, look at how it sparkles. How brilliant does it look? If a diamond is labeled as ideal cut, but it doesn’t have the sparkle and fire you’d like, then you should ask to see another diamond. (To really get a feel for the difference between an ideal cut and a non-ideal cut, ask to see one of each. You should be able to see a difference between how they sparkle.)
The most common shapes of diamonds today are:
• Round brilliant
o Most popular shape
o Most brilliant shape
o Most expensive shape
• Oval
o Like a round, but elliptical
o Very flattering to small hands
• Marquise
o Like an oval, but with pointed ends
o Flattering for small and large hands
• Pear
o A pear is a cross between an oval and a marquise
o Flattering to almost any hand
• Heart
o Like a pear, but with a cleft in the middle
o Make sure that both sides of the heart are equal
• Princess
o Rectangular
• Emerald
o Rectangular with cut corners
o This is a step cut, not a brilliant cut
While the round brilliant is the most common shape you see, not all women like it. This is one area where you really have to know what she likes and dislikes. If she really likes the emerald shape and you get her a heart, she may be disappointed. Keep in mind that the shape is the first thing that people tend to notice when they see a ring.
