Minerals

Everything that humankind consumes, uses, or produces has its origin in minerals. Minerals are the building materials of our technological civilization, and a single mineral may have many unrelated uses.

The mineral corundum provides a good example. Corundum is an extremely hard substance. Small bits of corundum are part of the rock called "emery" which has been used since ancient times as an abrasive, to cut and grind metal and stone. Pure corundum is still used for this purpose today. Another property of corundum is that it remains solid and stable at very high temperatures, well past the melting point of iron. Therefore, masses of small corundum crystals pressed together are shaped into "alumina" firebricks, crucibles, and other apparatus to use in furnaces. Corundum is also the basis of several gemstones.

Pure corundum is colorless. However, as is the case with many other minerals, trace amounts of metal in the stone impart brilliant colors. Rubies are corundum colored red by traces of chromium. Sapphires come in shades of blue, yellow, green and violet; these varieties of corundum contain traces of iron, titanium or other elements.

Finally, corundum is indirectly a major source of aluminum metal. The ore of aluminum, called bauxite, is a mixture of several minerals containing aluminum together with oxygen and hydrogen. The first step in releasing the aluminum from the other elements is to convert the bauxite to corundum.

Table 2 lists a wide variety of familiar materials and the minerals that compose them. These and most other minerals will find even wider usage in the future as research in the field of materials science continues.