"Give Us the Crystals . . ."

The diamond cutter sets his whirring wheel, dresses its edge with diamond dust and lubricant as it saws slowly into the big, water-clear crystal on the cutting stand. But the big crystal under the wheel is not a diamond. It is quartz, the most abundant of all minerals but a newly prized jewel of war. Once ground to size, it is the governor of ship, plane and tank communications, an indispensable monitor of the accuracy of range-finding instruments and fire-control devices.

The special ability of quartz crystals to generate an electric current when placed under stress was first observed by Hauey in 1782 and rediscovered in 1880 by Pierre Curie. It is called "piezoelectric effect" (from the Greek piezein: to press; literally, pressure electricity). Conversely, quartz crystals can translate electrical energy into mechanical movement. When an alternating current is fed through a slice of quartz it vibrates at a definite and unchanging frequency. The thinner the slice, the higher the frequency. It is like a tuning fork which sounds the same note no matter how hard or lightly it is struck, or like the escapement of a watch through which the changing power of the mainspring flows in measured ticks.

Wafers of Accuracy. Sawed into thin slabs, usually no bigger or thicker than a postage stamp, quartz determines a radio sending or receiving channel with hairbreadth accuracy. Tanks with quartz oscillators, for instance, can converse in battle without enemy interference, changing frequencies merely by changing crystals. Using quartz controls, radio stations stay on the beam; hundreds of conversations ride pickaback along a single telephone circuit and are properly unscrambled at the receiving end.

The uncanny accuracy of quartz crystals in frequency control demands unyielding accuracy in manufacture. The wafers must be cut with due attention to the structure of the mother crystal, must be ground to within a ten-thousandth of an inch.

Since Pearl Harbor the industry has expanded over 200 times. Diamond-cutting methods now used by most manufacturers have speeded up production, cut down waste. The best crystals come from inland Brazil, but WPB is pushing U.S. exploration. The Japs, incidentally, in 1930 bought up a tidy supply of quartz crystals which were an unwanted byproduct of California gold mining. Every Jap communications set captured so far has been quartz-equipped.

So important is the right kind of crystal that the Signal Corps last month set up a special inspection laboratory in Rio de Janeiro, and plans for the mechanization of quartz mining are well under way. The sentiments of the Signal Corps are visible in a big poster which hangs in many a cutting room. It reads, "GIVE US THE CRYSTALS AND WE'LL PUT THE ... -------ON THE RUN." In radio code the dots & dashes spell SOB.

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