David Foster, age 12, 8 Milwaukee, Wis., for his question:
HOW ARE DIAMONDS CUT?
Diamonds are crystals formed almost entirely of carbon. Most diamonds have eight sides which form a double pyramid, although some may have as many as 12 sides. Scientists say that diamonds were formed millions of years ago when carbon was subjected to great heat and pressure. The gems are among the most costly jewels in the world, partly because they are rare.
Hardest substance naturally occurring is the diamond. Because it is so hard, the diamond is one of the world's most enduring of all gem stones.
Diamonds are used in industry for cutting, grinding and boring. About 80 percent of the world's diamonds are suitable only for industrial use. The other 20 percent become stars on engagement or wedding rings, or crown other pieces of jewelry.
A diamond has great power to reflect light, bend rays of light and break light up into all the colors of the rainbow. But to produce the greatest possible brilliance in a diamond, many little sides, or facets, must be cut and polished on it.
It is also important that each tiny facet on a diamond is cut to exactly the right size and shape and that it be placed at exactly the right angle.
During the 1400s, diamond cutters learned how to shape and polish a stone by use of an iron wheel coated with diamond dust. As time passed, man learned more about diamonds and discovered the shapes which give the greatest brilliance.
Cutting of a diamond starts when a skilled craftsman saws a rough diamond in two. He uses a thin circular saw that holds diamond dust. The corners are then rounded by rubbing together a spinning diamond and a stationary one.
Next the cutter uses the lopping process to grind facets on the stone. Lopping involves carefully pressing the diamond against a rotating wheel coated with diamond dust.
The style of cut often seen today on a diamond is the round shape with 58 facets. This style is called the brilliant cut and it was first used in the 1600s.
Diamonds are graded according to weight, purity, color and cut. The weight of a diamond is measured by the carat, with one carat weighing 200 milligrams.
The purity of a diamond can be lessened by small cracks. The cut of a diamond affects its value because a stone that is not properly proportioned does not have as much brilliance as a stone that is well cut.
Cutting and polishing a rough diamond is an extremely slow and costly process. It must be done by highly trained workers who take many years to learn to do their work, skillfully.