1. Semester Exam Review
Rocks & Minerals

2. Rocks
The 3 types of rocks are:
Igneous
Sedimentary
Metamorpic

3. Igneous Rocks
Igneous rocks are formed when lava or magma cools and hardens.
Extrusive igneous rocks form when lava cools on the Earth's surface.
A volcano makes extrusive igneous rocks.

4. Pumice Extrusive igneous rock made of solidified volcanic ash.
Full of holes.
Floats on water.

5. Obsidian Extrusive igneous rock.
Lava cools in water so it solidifies quickly.
Also known as volcanic glass because it looks like glass.

6. Intrusive Igneous Rocks
Form when magma cools slowly under the Earth's surface.
Most intrusive rocks have large, well-formed crystals.
Examples include granite, gabbro, and diorite. All of these form under the Earth’s surface.

7. Sedimentary Rocks
Sedimentary rocks tell us what the Earth's surface was like in the geologic past.
They can contain fossils that tell us about the animals and plants or show the climate in an area.

8. Chemical Sedimentary Rocks
Form from chemical reactions in the oceans, seas, and lakes.

9. Organic Sedimentary Rocks
The sediment in an organic sedimentary rock is made of tiny fossils!
Sedimentary rocks are also important because they may contain water for drinking or oil and gas to run our cars and heat our homes.
Examples: chalk and limestone

10. Metamorphic Rocks Any rock can become a metamorphic rock.
Metamorphic rocks: rocks buried deep in the Earth that formed at high temperatures and under extreme pressure.

11. Nonfoliated Metamorphic Rocks
Identified on the basis of their composition:
Quartzite= composed of the mineral quartz, metamorphosed sandstone.
Marble=composed of the mineral calcite; metamorphosed limestone.

12. Minerals
Minerals are naturally occurring, inorganic solids with a definite chemical composition and a characteristic crystalline structure.
About 3,000 different minerals have been described.

13. Mineral Identification
Most minerals can be identified by their physical properties:
Color
Streak
Luster
Hardness
Cleavage
Fracture
Density
Crystal form).

14. Color
Some minerals are easily identified by color because they are never any other color.
But, chemical impurities can change the color of a mineral without changing its basic make-up, so it is not a very good way to identify a mineral.

15. Quartz
Quartz constitutes 12% of the Earth's crust and is used in countless products from computers and watches to satellites and medical equipment.

16. Luster Luster is the way the surface of a mineral reflects light.
There are two general types of luster – metallic (ex: gold) and non-metallic.

17. Hardness
Mohs Hardness Scale: Arrangement of 10 minerals into a sequence from 1-10.
1 is the softest mineral, 10 is the hardest mineral.

18. Fracture & Density
Not all minerals cleave easily, some fracture instead.
Fractures can be smoothly curved, irregular, jagged or splintery.
Each mineral has a unique density which can help to identify it.