Rocks and Minerals   May 20, 2008   2:00/1:00 MT/PT
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Girl Investigating a Rock Wall
Investigating Rocks and Minerals
In Your World
Photo of Rocks
      
     Rocks are all around us. You can see rocks inside your house, in your yard, on your street, on a country road, everywhere you look. Statues, chalk, marble, pencil lead, sandpaper, glass, tombstones, bricks, the walls of your room, mountains, pebbles, soil, a volcano are all rocks!! Rocks are used to build homes, an aluminum baseball bat, a washing machine, video games, airplanes, cars, and jewelry! Rocks aren't always solid. Sand and Mud are rocks. No matter where you are you are always close to rocks and minerals. They are fascinating and exciting so let's begin our investigation to learn more.
      

            We'll begin with a look at the structure of the earth because that is where all rocks come from. They have been on Earth for almost 4 billion years. Geologists record time with the Geologic Time Table.
    Structure of the Earth The Earth has 3 layers: the crust, the mantle and the core (which is  subdivided into the outer and inner core.) Each layer is unique and you can find the interesting details of the layers at:

Learning About
the Structure of the Earth
     

 
How do we classify rocks?
There are 3 main types of rocks depending on how they were formed in the different layers of the Earth.
They are: Igneous, Sedimentary, and Metamorphic.
Type of Rock
How it is Formed
Where it is Formed
Other Facts& Examples
rock weathered to many pieces of rock and soil which then settles into layers. The layers are squeezed together until they harden into rock.
where oceans, lakes, or other bodies of water exist or existed
layered, soft often containing fossils. limestone, chalk, coal, sandstone, shale
rock formed when melted rock cools and hardens
lava from volcanoes or magma that cools inside the Earth
often shiny or glossy. basalt, granite, pumice, quartz, obsidian
igneous, sedimentary, or other metamorphic rock that is changed by heat and pressure deep within the earth.

deep within the Earth

hard, often contains crystals, may have bands or layers marble, slate, gneiss, schist
     
The heads at Mt. Rushmore are carved out of an igneous rock called granite
Mt. Rushmore

The heat of lightning striking the sand of a beach can melt the sand to form a glassy rock called "fulgurite."

     
      A rock can begin as one type and can change many times. In fact, rocks are always changing. However, the changes happen so slowly that they are difficult to see. We have seen above that heat and pressure can change rocks which then break down by weathering and move by erosion. It can take thousands of years for rocks to weather and erode. This process of changing is called the  rock cycle.
 

     
Weathering
is the process that breaks rocks down into smaller pieces. Weathering can be caused by: wind, rain, ice, running water, plant roots, chemicals, freezing and thawing.

Rock warning sign
      
Erosion
is the movement of rock pieces from place to place. Erosion can be caused by: wind, rain, running water, waves, gravity, and moving ice.
What else do we know about rocks?
A rock is a material made of one or more minerals.
What is a Mineral?
     Minerals are made from 92 elements that join together in many different ways. Some minerals are made of only one element, such as silver. Most are a combination of two or more elements, such as granite which is made of quartz, feldspar, mica. Scientists have identified over 3,000 minerals. The particles of minerals are arranged in a repeating pattern called a crystal.
      Recognizing a mineral is not an easy job. There are several different properties of minerals and tests that are used to identify them. The properties are: luster, hardness, color, streak, cleavage, crystal shape, and magnetism. Challenge yourself to identify minerals.

Mineral names and uses
Don't miss the amazing crystals at the Smithsonian Gem & Mineral Collection.
The mineral, salt, was so valuable in Factancient times that it was traded ounce for ounce for gold
azurite(blue) malachite(green)
The blue color is the mineral "azurite." The green color is "malachite."

Fact
Diamond is the hardest mineral.

Fact
Meteorites, rocks from space, help scientists learn about the solar system.
 

     This is just the exciting beginning of your investigation. At Links for Rock Hounds meet Rocky and Rex, solve mysteries, be inspired by beautiful photos of rocks and minerals, and discover more as you learn how to think like a geologist and mineralogist.

 
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