1. CLASSIFYING ROCKS P
4.1

2. STUDYING ROCKS GEOLOGISTS LOOK AT SEVERAL CHARACTERISTICS:
1. MINERAL COMPOSTITION
2. COLOR
3. TEXTURE

3. MINERAL COMPOSTITION
ROCKS ARE MADE OF MIXTURES OF MINERALS AND OTHER MATERIALS. ABOUT 20 MINERALS MAKE UP MOST OF THE EARTH’S CRUST. THESE ARE KNOWN AS THE ROCK-FORMING MINERALS.

4. COLOR
A ROCKS’ COLOR PROVIDES CLUES AS TO WHICH MINERALS ARE IN THE ROCK.
BASALT- A DARK COLORED ROCK THAT IS LOW IN SILICA
GRANITE- A LIGHT COLORED ROCK HAS HIGH AMOUNTS OF SILICA
REMEMBER COLOR DOESN’T TELL US MUCH.

5. TEXTURE VERY USEFUL FOR IDENTIFYING.
GRAINS ( PARTICLES OF MINERALS) GIVE ROCK THEIR TEXTURE OR FEEL AND LOOK OF ROCK’S SURFACE.
SMOOTH, GLASSY, CHALKY, ROUGH,
ALSO USE SIZE SHAPE AND PATTERN OF GRAIN.

6. GRAIN SIZE
IF A GRAIN IN A ROCK IS LARGE AND EASY TO SEE IT IS CALLED COURSE- GRAINED.
FINE-GRAINED IS SO HARD TO SEE YOU WOULD NEED A MICROSCOPE.
\SOME HAVE NO VISIBLE GRAIN EVEN UNDER A MICROSCOPE.

7. GRAIN SHAPE
SOME GRAINS ARE ROUNDED AND SOME ARE JAGGED.

8. GRAIN PATTERN SOME GRAINS FORM PATTERNS.
THEY CAN LIE IN FLAT LAYERS OR STACKS . SOME SWIRL. SOME HAVE DIFFERENT COLOR BANDS.
BANDED/ NONBANDED.

9. HOW ROCKS FORM
WE WANT TO DETERMINE A ROCK ORIGIN. WE CLASSIFY ROCKS INTO CATEGORYS BASED ON WHERE THEY FORMED.
IGNEOUS- MAGMA OR LAVA
METAMORPHIC-HEAT/PRESSURE
SEDIMENTARY-CEMENTED/COMPACTED/BURIED

10. What are minerals made up of and how do they form?

11. What are minerals made up of?
Minerals are made up of elements or compounds. Elements are atoms that are all alike and have the same number of protons, neutrons, and electrons. Some minerals are compounds which are combinations of different elements.
Reminder atoms have a nucleus and an electron cloud.

12. The atom Protons and nuetrons are in the nucleus.
Electrons are in the electron cloud.

13. Mineral crystals
I know that it is a stretch to get from atoms to minerals but minerals are made up of tiny atoms and when they bond together- they form minerals. They also form into 6 particular shapes or patterns.
Cubic, hexagonal, etc

14. Crystallization
Crystal come in many sizes. Some are geodes which are a rounded hollow rock lined with mineral crystals.
They form when water seeps into the rock and slowly evaporates leaving the minerals behind to crystallize. Crystallization is the process by which atoms arrange themselves into a pattern.

15. 2 ways minerals cystallize
1. from molten material
2. from being dissolved in water

16. Minerals from magma and lava
Magma-molten material inside the earth
Lava- magma that reaches the surface.
Anytime magma cools whether inside the Earth or as lava, minerals crystallize. The size of the crystals depend on the rate of cooling.
Cools slow- large crystals
Cools fast- small crystals

17. Minerals from solutions
A solution is a mixture in which one substance is dissolved into another substance.
Mineral crystals can form this way underground or in bodies of water on Earth’s surface either by evaporation or from hot water solutions.

18. Evaporation
When minerals are left behind after water evaporates then crystals form
Examples:
Halite
Gypsum
calcite

19. Hot water solutions
Magma heats water underground and causes minerals to dissolve in the water, when this water cools the elements and compounds leave the solution and crystallize.
Pure metals form veins or narrow chambers or slabs of minerals. They often form in cracks in the rock surrounding it.