Site map Contact Us Search Home
 :: Home : Education Center : Geology 101
 A Closer Look at Rocks

You may not realize it, but there's more to rocks than meets the eye. All rocks are not the same and, in this business, it is important to understand the differences between them. So, let's talk about the science behind the rocks under your feet!

What is geology? Geology is the study of the earth's history, the materials that make the earth and how these materials change over time. There are hundreds of kinds of rocks covering the earth. These rocks are divided into three classes.

(Click on rocks for larger image)
 

Igneous rocks are very hard and form from the hardening of rock in its molten state, such as lava from volcanic eruptions.

TrapRock
Trap Rock

Gabbro
Gabbro

Pegmatite
Pegmatite

Granite
Granite

 
 

Metamorphic rocks form from other rock that has been exposed to extreme heat and pressure over millions of years to eventually form new minerals.

Quartzite
Quartzite

Slate
Slate

Amphibolite
Amphibolite

Marble
Marble

 
 

Sedimentary rocks form from the accumulation of sediments in water or from the air. Sediments are rock particles, animal remains, plant remains or a mixture of all three. Sedimentary rocks have several layers that can be seen.

Limestone
Limestone

Siltstone
Siltstone

Shale
Shale

Sandstone
Sandstone


© 2013 Martin Marietta Materials, Inc. All rights reserved. Terms of Use