What is a rock?A rock is a naturally occurring solid substance that

is normally made of minerals.

Some rocks are made of only one mineral. Others are made of several minerals combined.

By figuring out what minerals are in a rock andunderstanding how they are formed geologist

place rocks into one of three groups:Igneous metamorphic sedimentaryand .

What is a mineral?Minerals are the building blocks of rocks.

Scientists have discovered over 3,000 types of minerals!

A mineral is a natural, nonliving substance.

Properties of mineralsColor: Color alone, cannot identify minerals. Many minerals have the same color. Quartz can be many different colors!

Hardness: refers to a minerals ability to scratch another mineral or be scratched. The MOHS’ Scale shows the hardness of some common minerals. Each mineral has a number one - ten. Ten is the hardest kind.

Luster: refers to the way light bounces off the surface of a mineral. Some have a metallic, or shiny luster. Minerals with no shine at all have a dull luster.

Streak: If you scratch a mineral along a white tile, it leaves behind a powder. A minerals streak is the color of that powder. The streak may be different from the color of a mineral’s surface!

Properties of minerals

mineral mica feldspar hematite pyrite

colorwhite, green,

silver, or brown

white, pink, gray, or smoky black

gray or brown

gold or brassy yellow

luster pearlydull or glassy

metallic or dull

metallic

streak white white red green-black

hardness 2 - 2.5 6-6.5 6-6.5 5-6

Igneous RocksBelow earth’s surface are areas of melted

rock called magma. When magma cools and hardens, igneous rocks form.

Igneous rocks can also form from lava above earth’s crust.

The texture of an igneous rock depends on how fast the magma cools to form the rock.

The slower it takes to cool the more mineral grains will form. If it cools quickly, the rock will have a smoother, glassy texture.

obsidian

basalt

granite

Sedimentary Rocks

Sedimentary rocks are formed from sediments that are pressed and cemented together.

These layers are made of tiny pieces called sediments.

Some sediments are formed from rocks or minerals. Others are bits of plants,

shells, or other hard materials.

It can take millions of years for sediments to become rocks!

metamorphic Rocks

A metamorphic rock is a rock that is formed from other rocks by extreme heat and pressure.

When rocks are under extreme heat or pressure (like under earth’s surface!)

their physical appearance can change.

granite gneiss

The Rock Cycle