Ruby

Splashery stretches a drumhead over this Splash's outline, twelve inches across, and finds the ways it can ring. Its lowest is 452.9 Hz, 50 cents sharp of A4. The next fifteen are its overtones, and each one draws its own figure: sand gathers on the lines that stay still.

Tap it to make it glow deep red.

A ruby is a red form of the mineral corundum, which is made of aluminum and oxygen. A little chromium in the crystal gives it its red color. Corundum is very hard, second only to diamond among gems, and in any other color it is called sapphire.

The chromium also makes rubies glow red under ultraviolet light. Tap it and the stone lights up deep red from its heart outward, throbs twice and fades. In 1960 the first laser was made with a rod of ruby.

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