Diamonds are harder than anything else in the world. But crystals of carborundum are almost as hard. "Carborundum" is a trade name. Scientists call carborundum "silicon carbide."
Diamonds are dug out of the ground. Carborundum crystals have to be made. Carborundum was invented accidentally in 1891 by Edward Goodrich Acheson. The inventor was trying to make diamonds.
Today carborundum crystals are made in electric furnaces out of a mixture of sand and coke. The mixture is heated very, very hot. The temperature inside the furnace has to be more than 3,500° F. to make the crystals form.
Near Niagara Falls there is a big plant for making carborundum. Electricity for the furnaces comes from a power plant in which the generators are driven by water power. Operating the furnaces costs less than if the current came from generators driven by steam engines.
Carborundum is useful for grinding and polishing other hard materials. It is crushed into fine grains before it is used. Sometimes solid wheels and other tools for grinding and polishing are made of it.
