• Rocks are classified by how they formed and what they’re made of

• There are 3 general classes of rocks:– Igneous–Sedimentary–Metamorphic

Are formed when lava and magma cool to form solid rock

• Extrusive: are formed once magma reaches the surface (lava) and cools – Ex: basalt, pumice

• Intrusive: are formed from magma that cools and solidifies within the crust, which may later be uncovered by the process of erosion – Ex: granite gabbro

Are formed when sediments (sand clay, and silt) are compressed and

become solid rock

• Formed by wind, water, snow or organisms breaking down other rocks into sediments

• Most sediments are deposited on the bottom of lakes, rivers and seas, and then compressed to form rock.

• Cover about 75% of Earth’s surface• Many sedimentary rocks have been moved

by water, wind, waves, currents, ice or gravity.

sandstone

limestone

chalk

shale

Halite (rock salt)

coal

Common examples

Metamorphic rocks form when existing rocks are heated or squeezed; they recrystallize and might change chemically.

• All kinds of rocks can be changed• Can change the crystal structure, texture,

or can form new minerals

gneiss

marble

limestone

granite

In the rock cycle, rocks change from one type to another over millions of years.

A rock in any part of the cycle could become any other kind of rock.

Igneous Rocks

Sedimentary

Rocks

Metamorphic

Rocks

Sediments

Magma

Heat and Pressure

Melting

Cooling and Hardening

Weathering and Erosion

cementation

A mineral is an inorganic solid material with a particular chemical makeup and orderly arrangement of atoms.

• Rocks are usually composed of two or more minerals.

• Minerals form from hardening of magma or lava

• Mineral formation clues include size and how mineral crystals fit together.

• Solid materials with a repeating pattern of atoms are called crystals.

• Cleavage- splitting into thin sheets

• Fracture- breaking into rough edges

• Color- many different colors, not mineral specific

• Shape (habit)- special arrangement of atoms, if grown unimpeded

• Luster- describes how light reflects from a mineral’s surface.

• Streak- is the color powder produced when a mineral is scratched on an unglazed white tile.

• Hardness- Moh’s scale is used to classify minerals from 1 (softest, talc) to 10 (hardest, diamond). It is also a test of which minerals scratch or are scratched by others.

• Other properties of minerals include: magnetism, double refraction,

taste, or reactions with acid.

Rare minerals which can be cut and polished are gems. This makes them ideal for jewelry.

An ore contains enough useful mineral to be sold at a profit. Copper is an example of an ore.