Minerals and Gems
Minerals are solid, inorganic (not living) substances that are found in and on earth. Most are chemical compounds, which means they are made up of two or more elements. For example, the mineral sapphire is made up of aluminum and oxygen. A few minerals, such as gold, silver and copper, are made from a single element. Minerals are considered the building blocks of rocks. Rocks can be a combination of as many as six minerals.
Many minerals, such as gold and silver, are very valuable because they are beautiful and rare. Limestone, clay and quartz are other examples of minerals.
Gems are minerals or pearls that have been cut and polished. They are used as ornaments, such as jewelry. Precious stones are the most valuable gems. They include diamonds, rubies and emeralds