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Rocks

http://geology.com/rocks/

+Why study rocks?

Rocks are the pages in the history book of the earth. They tell stories of times long past. From rocks, we have learned of dinosaurs, trilobites and thousands of other life forms that existed on earth once but are now no more.

We have learned that the earth is constantly moving, shifting, and changing. Rock is continually being created. It is heated, squeezed, and weathered into new rocks. Finally, it is remelted to start the process anew. By studying rocks, we learn to read the pages of earth’s history.

+What is a rock?

A rock is:

A solid Naturally occurring Is made up of minerals or mineral like matter.

Rocks are classified by how they are formed. There are three basic groups

+Igneous

• Igneous rocks form when molten lava (magma) cools and turn to solid rock.

• Obsidian is nature’s glass. It forms when lava cools quickly on the surface. It is glassy and smooth.

• Pumice is full of air pockets that were trapped when the lava cooled when it frothed out onto the surface. It is the only rock that floats. 

+Sedimentary Rock

• Over time the layers of sand and mud at the bottom of lakes & oceans turned into rocks. These are called sedimentary rocks.

• Some examples of sedimentary rocks are sandstone and shale.

• Sedimentary rocks often have fossils in them.

+Metamorphic Rock

• Metamorphic rocks are rocks that have changed due to heat and/or pressure.

• Metamorphic rocks were originally igneous or sedimentary, but due to movement of the earth's crust, were changed.

• Marble and slate are examples of a sedimentary rock that has been changed into a metamorphic rock.

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Rock is continually being created. It is heated, squeezed, and weathered into new rocks. Finally, it is remelted to start the process anew

+Slate metamorphic

Slate is a metamorphic rock that forms from mudstone or shale.

The color of slate is largely determined by the amount of iron it contains, but it is normally a shade of gray.

Slate can easily be broken into neat, thin sheets because of its foliation.

Used to be used as a chalkboard in schools.

+Shale sedimentary

Shale rocks are a type of sedimentary rock.

They are usually found in areas where gentle waters have deposited sediments that become compacted together.

Shale usually forms in sheets.

It is usually a gray color.

+Marble metamorphic

Marble is a metamorphic rock that forms when limestone is subjected to heat and pressure.

It is composed primarily of calcium carbonate.

Our marble is a light color. You can see the crystals inside make it sparkle.

+Limestone sedimentary

Limestone rocks are sedimentary rocks that are made from the mineral calcite which came from the beds of evaporated seas and lakes and from sea animal shells.

This rock is used in concrete and is an excellent building stone for humid regions.

Our limestone is a light gray color.

You can see little crystals inside.

+Limestone (Fossils) sedimentary

Limestone rocks are sedimentary rocks that are made from the mineral calcite.

This came from the beds of evaporated seas and lakes and from sea animal shells.

This limestone looks like the conglomerate because it has little pieces of fossils inside.

+Obsidian igneous

Obsidian rocks are igneous rocks that form when lava cools quickly above ground.

Obsidian is actually glass and not a mixture of minerals. The edges of this rock are very sharp.

It is a shiny black rock.

+Conglomerate sedimentary

Conglomerate rocks are sedimentary rocks.

They are made up of large sediments like sand and pebbles. The sediment is so large that pressure alone cannot hold the rock together.

It is cemented together with dissolved minerals.

+Granite igneous

Granite rocks are igneous rocks which were formed by slowly cooling pockets of magma that were trapped beneath the earth's surface.

You can see large crystals that shine in the rock.

Granite is used for long lasting monuments and for trim and decoration on buildings.

Granite comes in different colors depending on the mineral content. This granite is pink.

+Pumice igneous

Pumice rocks are igneous rocks which were formed when lava cooled quickly above ground.

You can see where little pockets of air had been. This rock is so light, that many pumice rocks will actually float in water.

Pumice is actually a kind of glass and not a mixture of minerals.

It is often light in color.

+Basalt igneous

Basalt is a dark-colored, fine-grained, igneous rock

As it turns out, most of the ocean floor is basalt, and most of the continents are granite.

This is also abundant on the moon.

Among other characteristics rocks are generally dark in color and often have holes where pockets of air have been.

+Coal sedimentary

Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment.

Light, shiny black rock

Used for energy. It is a fossil fuel.

+Quartz (Mineral)

Quartz is a very common mineral.

Quartz is the most common mineral found in rocks.

Looks like clear glass or a crystal

Quartz is very important in industry for making gauges, oscillators, resonators and watches.