Rock makes up the earth's . Mountains, coastlines, valleys and are made up of different kinds of rock. In many areas tiny pieces of eroded rock forms , on which plants can grow. Most rocks contain crystals of two or more different . Granite for example contains grains of quartz and feldspar.

Rocks play a major role in the construction industry. , for example, is made up of stones, sand and gravel and mixed with cement. Rocks are also used to make medicine, and cosmetics. Sandstone and have been used to make historic monuments, like the ancient Egyptian pyramids.

Rock can contain that are extracted. This type of rock is called . Iron, copper, lead, gold, and uranium are among the most important metals than can be dug out of ore. Other rocks contain valuable minerals, like diamonds or other .

are scientists who study the origin and of rocks. The information they get reveals a lot about the history of our planet. Rocks also contains and shows how life evolved and which events shaped the Earth and the solar system.

Rocks are often classified by their . Soft rocks can be scratched with a fingernail, hard rocks ,like diamonds are used to cut glass and other rocks as well as in the oil drilling industry.

Rock is formed and reformed in a . Wind, glaciers and rivers transport rock, break them into tiny pieces and them in faraway places where they turn into . Through pressure such rock sinks deeper and deeper and turns into rock. When rock comes to the surface again it in the form of volcanoes. The cycle then starts from the beginning.