Minerals are useful in many industries in the past
and today. A major industry that most people think about is the gem
mineral industry. Minerals that are used for gems are usually hard.
People love to purchase jewelry to wear or to give as presents. The very
symbol of a marriage engagement in the United States is a diamond. This
is not true in many other countries. However, a gold ring, as a symbol
of marriage is used in many cultures.
Many gems are the same mineral but different color
for example a ruby (red) and sapphire (blue) are the mineral corundum.
Emerald (green) and aquamarine (blue) are the mineral beryl. Peridot
(green) is the mineral olivine. Quartz probably has the most varieties
of gems because it comes in many coloring including amethyst (purple),
agate (multicolored), and tigerís eye (brown-yellow).