At one time or another, you have probably held a rock in your hand. Recall the texture. Was it smooth, polished by the force of sand and salt water pounding it onto the beach? Was it rough and cragged, left exposed for centuries to the wind and sun of a canyon wall? Recall the color. Was it coral and pink, like the colors of Bermuda's sand? Was it fiery red, like the colors of Arizona's canyons? Recall the size. Was it a handful, heavy with the weight of being worn? Was it a tiny pebble, a small fragment broken off from what it once was?

Rocks are our world. The planet Earth is, essentially, just one big interesting rock, sometimes called "the third rock from the sun." The multi-faceted rock we live on supports life in many ways. The deep oceans, the vast deserts, and the high mountains, are just a few of the ways rock emerges and supports life.

Rocks remember. Geology is the science and study of the earth and its life, especially as recorded in rocks. Rocks, then, keep record of the passage of time and the evolution of living things.

The word rock refers to solid mineral deposits. Rocks are minerals, but not all minerals are rocks. Minerals are all substances that can't be classified as "animal" or "vegetable." Metals ores found in the earth, like gold and silver, are minerals. Crystalline substances, like salt and quartz, are minerals. Homogeneous natural substances, like water and gas, are also minerals. These non-solid minerals, however, are not considered "rock."

Begin with Minerals
Minerals are classified in several "classes" based upon common properties or characteristics. Explore the diversity of minerals as preparation for thinking about rock. The alphabetical listing of minerals by name quickly shows how diverse minerals really are. Specimens, on display at The Geology Museum, range from the most common to the extremely rare. The Mineral Gallery offers both descriptions and a growing collection of images.

Information provided by: http://www.fi.edu