TYPES OF ROCKS

Types of Rocks

• Igneous
• Metamorphic
• Sedimentary

ROCK CLASSIFICATION

• Rocks are a combination of one or more minerals or organic matter
• Many rocks are made up of mostly quartz and feldspar, which are made of the compound silica
• The size, shape and positions of the grains that make up a rock determine texture

IGNEOUS ROCKS

• Forms when hot, liquid magma cools into solid rock
• Intrusive - forms by magma that pushes into surrounding rock below Earth's surface Ex. Granite
• Extrusive - forms when lava erupts onto Earth's surface Ex. Obsidian

SEDIMENTARY ROCKS

• Forms by weathering, erosion, deposition, burial, and cementation
• Clastic - forms when sediments are buried and compacted together by calcite or quartz Ex. Sandstone
• Chemical - forms when water, usually seawater, evaporates Ex. Halite

SEDIMENTARY CONT.

• Organic - forms from the remains or fossils of dead organisms Ex. Coal

METAMORPHIC ROCKS

• Forms by exposure to high temperature and pressure
• Foliated - forms by metamorphic process in which mineral grains are arranged in planes or bands Ex. Gneiss

METAMORPHIC CONT.

• Non-foliated - forms by high pressure and temperature Ex. Limestone/Marble