1. Types of Rock

2. What are Rocks?
A rock is a naturally occurring solid mixture of one or more minerals, volcanic glass and or organic matter
Rocks are classified by how they are formed, their composition, and texture
Rocks change continuously over time through the rock cycle

3. Igneous Rocks Igneous rock begins as magma. Magma can form:
When rock is heated
When pressure is decreased
When magma changes composition
Magma freezes (solidifies)
between 700 °C and 1,250 °C
Magma is a mixture of
many minerals

4. Igneous Rocks
Felsic: light colored rocks that are rich in elements such as aluminum, potassium, silicon, and sodium
Mafic: dark colored rocks that are rich in calcium, iron, and magnesium, poor in silicon
Coarse-grained: takes longer to cool, giving mineral crystals more time to grow larger
Fine-grained: cools quickly with little to no crystals formation

5. Igneous Rocks
Intrusive Igneous Rocks: magma cools below the Earth’s surface forming mineral grains (crystals)
Extrusive Rocks: forms when magma erupts onto the Earth’s surface (lava), cools quickly with very small or no crystals formed

6. Igneous Rocks Coarse-Grained Fine-Grained Felsic Granite Rhyolite
Mafic
Gabbro
Basalt

7. Mafic, fine grained, extrusive
Obsidian
What is Obsidian?
Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form.
Igneous Rocks
Obsidian is a dark-colored volcanic glass that forms from the very rapid cooling of molten rock material. It cools so rapidly that crystals do not form.
Is this rock Felsic or Mafic?
Is it fine-grained or coarse-grained?
Is this rock Intrusive or Extrusive?
Mafic, fine grained, extrusive

8. Sedimentary Rocks Sedimentary rock is formed by weathering
rock and forming sediments
Sediments are moved from one
place to another by erosion
Sediments are deposited in layers,
with the oldest layers on the
bottom
The layers become compacted and
cemented together with natural cements such as
quartz or calcite

9. Sedimentary Rock
Sedimentary Rocks are formed at or near the Earth’s surface
No heat involved
Strata – a layer of rock
Stratification – the process
in which sedimentary
rocks are arranged in layers

10. Sedimentary Rock
Clastic – made of fragments of rock cemented together with calcite or quartz
Conglomerate Breccia

11. Sedimentary Rock
Chemical sedimentary – minerals crystallize out of solution (liquid) to become rock
Halite Gypsum

12. Sedimentary Rock
Organic sedimentary – has remains of plants and or animals
Limestone Coal

13. Metamorphic Rock Metamorphism : to change shape
Minerals changes with heat and
pressure, they are flatten by being
partially melt and squeezed
Temperatures ranges between
150°C and 1,000°C
Usually takes place deep in
the Earth or near the edge of magma

14. Metamorphic Rocks Contact Metamorphism – heated by nearby magma
Increased temperature changes the composition of the rock, minerals are changed into new minerals
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15. Metamorphic Rocks
Regional Metamorphism – pressure builds up in rocks that is deep within the Earth
Large pieces of the Earth’s crust collide and the rock is deformed and chemically changed by heat and
pressure

16. Metamorphic Rock Foliated - contain aligned grains of flatten minerals
Gneiss is foliated metamorphic rock that has a banded appearance and is made up of granular mineral grains. The
Parent rock is granite
It typically contains abundant quartz or feldspar minerals.

17. Metamorphic Rock
Non-Foliated – mineral grains are not arranged in plains or bands
Marble is a non-foliated metamorphic rock that is produced from the metamorphism of limestone.
It is composed primarily of calcium carbonate.

18. Metamorphic Rock
Determine if the following rock samples are foliated or non-foliated:
Amphibolite
Quartzite
Phyllite
Non-foliated
Non-foliated
Foliated

19. Index Minerals
Index minerals can indicate the temperature and pressure at which the rock formed
Garnet forms at 700°C to 1200°C and
25 to 60km depth
Mica Schist forms at 700°C and
5 to 34km depth
Chlorite forms 400°C and 4 to 32km depth

20. Parent rock
Parent rock is the original rock type before the metamorphic rock formed
Granite Heat/Pressure Gneiss

21. Slate
Shale Heat/Pressure Slate

22. Marble
Limestone Heat/Pressure Marble

23. Quartzite
Sand Heat/Pressure Quartzite

24. Schist
Mica Heat/Pressure Mica Schist

25. Soapstone/Talc
Dolomite Heat/Pressure Soapstone