R-O-C-K-S
The Earth's building materials are the rocks. Rocks are a combination of minerals in varying proportions. A rock may be made of one or more minerals. Pure sandstone, for example consists only of the mineral quartz. Granite is composed chiefly of three minerals, quarts, feldspar and mica.
There are large deposits of granite in some areas of the country.
Photo taken by Jacquie Eastland.
This is a picture of one of the largest deposit of granite in the world, known as the Enchanted Rock. This scene is located in the Hill Country of Texas. A "recipe" with different mineral ingredients results in a different kind of rock. See a related article Enchanted Rock and Field Rocks
The solid crust of the Earth is rock. The soil itself is made up largely of rock which has been broken down by weathering. Beneath the Earth's solid crust are pockets of molten rock, called magma.
Certain hard substances formed from the remains of animals and plants are also called rock. Coal, which is composed of plant material, is an example. Limestone contains the shells and skeletons of sea creatures and limy masses built by plants.
Food is grown in soil, which is weathered rock. One kind of rock is eaten every day. This is salt, a rock composed of the mineral halite. Granite, limestone, sandstone, slate and marble are rocks known as building stones. They are removed from the earth by quarrying.
Buried treasure lie in the rocks. Some of their minerals are highly valued jewels such as diamonds, emeralds, and rubies. Gold, silver, iron, copper and the miracle metals of the atomic age, uranium and thorium, are among the mineral essential to modern civilization. These are taken from the earth by mining, one of the world's great basic industries.
Rocks tell a fascinating story of the origin and history of the Earth. A story that goes back millions of years. They tell of giant explosions; of mountains that rose from the sea and then were worn down to plains; of seas that invaded the land and then retreated or dried up. They tell of blankets of ice and of buried forest that turned to stone. The scientists who can read this story of the Earth are called paleontologists.
All rocks fall into one of three groups, according to how they were formed. These groups are igneous, sedimentary and metamorphic.
Other types of rocks are limestone, rock salt, coal, and different jewels.
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Revised 05/26/2007
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