George Jones Jr., age 13, of Harrisburg, Pa., for his question:
HOW HARD ARE DIAMONDS?
Diamond is the hardest natural occuring substance known to man. Because of its hardness, the diamond is the most valuable and enduring of all gemstones.
Minerals are arranged on a scale of hardness by scientists. The scale runs from 1 to 10, with 10 representing the hardest. The diamond and borazon are the only minerals that rate No. 10.
Borazon, by the way, is an artificially produced crystal that has the hardness of a diamond. Borazon can withstand temperatures of more than 3,500 degrees Fahrenheit while diamonds burn at 1,600 degrees Fahrenheit.
Not too many of the world's diamonds are of high enough quality to be used in jewelry. Eighty percent of the world's total are suitable only for industrial use.
Industrial diamonds include stones that are imperfectly formed, contain flaws or have poor color. They are necessary to industry because manufacturers of automobiles, airplanes and other kinds of engines and machinery began to use harder metals and to design engines and motors that require greater accuracy in shaping the parts. Only diamonds can be used in such work because of their extreme hardness.
Diamonds are used in industry to cut, grind and bore very hard metal quickly and accurately. Sometimes whole rough diamonds are set into industrial tools. Other times the diamonds are crushed and the diamond dust is baked into the tools.
Sometimes diamonds are cut to some special shape before they are set into tools. Diamonds are set in the ends of drills used in mining. Very fine wire is drawn to size through diamonds in which tapering holes have been cut.
Man made industrial diamonds are much in demand today because the need for the hard stones cannot be met by the supply of natural diamonds.
Diamonds, both man made and natural, have also found their way into the world of music. A permanent, almost indestructible hard diamond needle is used in just about all record players today.
Man made diamonds were first produced in 1955 by scientists at the General Electric Research Laboratory. They were tiny stones made by compressing carbon under great pressure and heat. In 1970 a team from the same company turned out the first man made diamonds of gem size and quality.
Man made stones are not usually sold as jewelry because they cost so much more to produce than the natural diamonds cost.
Imitation diamonds are jewelry items that are made to resemble genuine diamonds. However, they do not have the hardness of real diamonds and therefore soon show scratches and other signs of wear.
Researchers have discovered that by adding boron to diamonds, they turn into semiconductors. Semiconductors are materials with special electrical properties. They are used to make transistors and other electronic equipment.