Minerals and Rocks Chapter 8

Mineral Crystals Earth’s crust is made of rock All rocks are made of minerals Minerals – are natural, nonliving solid crystals that make up rocks Each minerals has crystals made of one shape, they also have the same chemical makeup Scientists have identified 3,000 minerals Rocks in the Earth’s crust are only made of a few called “rock-forming” minerals

How to Identify a Mineral Scientists use some of it’s physical properties: Color Luster Hardness Streak Cleavage

LUSTER Luster – is the way its surface reflects light It can be dull, metallic, pearly, glassy, greasy, or silky

HARDNESS Hardness – finding out how easily a mineral can be scratched They use a special chart called the Mohs Scale for Hardness A greater number can scratch all minerals with a lower number

STREAK streak – the color of the powder that a mineral leaves when it is scratched on a special plate Always the same color even if the mineral differs

Layers of Rock sediment – eroded materials that settles on land or on the bottom of lakes, rivers, and oceans Some are smooth and round, others have sharp corners New layers press on old ones They harden and form sedimentary rocks

Types of Sedimentary Rocks One type is made of materials that were once living things Limestone is made of hard skeletons and shells of sea animals that lived long ago Sandstone made up of bits of quartz that are the size of a grain of sand Mudstone forms in lakes or oceans where tiny particles settle

How Rocks Change into Soil Loose rocks at Earth’s surface and beneath it take a beating Freezing water, plants roots, and Earth’s natural processes break apart the rock These little pieces are ingredients in the soil Soil is full of dead and decaying plant and animal remains too

How Rocks Tell a Story sediment – eroded materials that settles on land or on the bottom of lakes, rivers, and oceans

How a Fossil Forms sediment – eroded materials that settles on land or on the bottom of lakes, rivers, and

Igneous Rocks sediment – eroded materials that settles on land or on the bottom of lakes, rivers, and

Metamorphic Rocks sediment – eroded materials that settles on land or on the bottom of lakes, rivers, and

The Rock Cycle sediment – eroded materials that settles on land or on the bottom of lakes, rivers, and