Earth Science: Chapter 2

Earth Science- Chapter 2

What is a mineral? A naturally occurring homogenous solid substance that is inorganic. Everything organic has complex carbons; therefore a mineral has no complex carbons.

3 different forms of mineral:
1. Element- mineral is made of 1 element. This is the simplest form of a mineral. Ex. mineral graphite.
2. Compound- more than 1 element is combined chemically in a specific ratio. Ex. Quartz= silicon + oxygen.
3. Mixture- different elements are mixed together, but there is no formula for it.

There are 3,000 different minerals on earth, however 98% of earth (troposphere, hydrosphere, atmosphere and lithosphere) is made up of just 12 basic minerals (see reference table).

Mineral Classification-
1. Color-
a. Distinct colors. Ex. gold.
b. Similar colors. Ex. gold and fool’s gold.
c. Many times, a white or colorless mineral will get discolored because of impurities.
2. Luster- how much of the light is going to be reflected off it.
a. Metallic luster- hard and shiny like metal.
b. Non-metallic- not so much light is reflected
1. Earthy- dull
2. Glassy
3. Pearly
4. Waxy
3. Streak- color of the powder of the mineral. This is very accurate because the streak will keeps its original color no matter what color change the rock may undergo. To find the streak, you take a streak plate (white porcelain plate) and rub the rock against it.
4. Crystal Structure- a crystal structure is atoms that are organized in a specific pattern:
a. Hexagonal- 6 sided crystal structure.
b. Rhombohedral- you can break off pieced in the direction of the two sides and the top.
c. Cubic- the mineral breaks off in cubes or rectangles.
d. Sheets- comes off in sheets.
e. Mineral breaks in to thin fibers.
5. Hardness- minerals may vary in their hardness. Hardness is tested relative to other minerals.
Mr. Moh set up Moh’s scale. It is a scale of 1- 10, where 1 is the softest mineral- talc, and 10 is the hardest mineral- diamond. You take the unknown mineral and scratch it. If it can’t scratch, it’s softer than the unknown mineral and if it does scratch, it’s harder than the unknown mineral.
6. Cleavage and fracture- how does a mineral break? Either with:
a. Cleavage- when a mineral brakes in a specific direction. The direction in which it breaks is the cleavage plane- same direction as the crystal structure.
b. Fracture- doesn’t break along the crystal structure. It’s jagged and splintered.
7. Density-
a. Mass/ density
b. Floatation- we see if it floats in a liquid. If it floats, it’s less dense and if it doesn’t float, it’s denser.
Water is 1 g/cm³. Based on the density of water, you can discover the specific gravity of the mineral.

6 minerals that have specific characteristics:
1. Calcite- colorless mineral. If you look through it, you’ll see words double. It also bubbles in acid.
2. Uranium- Extremely radioactive.
You can check it with a Grieger counter (GM counter)- the more radioactive something is, the greater the increase on the scale.
3. Magnetite- magnetic.
4. Talc- soapy.
5. Graphite- greasy.
6. Halite- salty.

Rocks-

Earth is made up of rocks. Some rocks have organic matter- remains of plants and animals.

Rocks are classified according to their origins. They could’ve been made and formed in 3 different ways:
1. Igneous- result of magma and lava becoming solid. They are the only rocks made from a hot liquid. When the magma or lava cools down to the temperature of solidification (between 600- 1000ºC), it’ll begin to solidify and crystallize. Based on how quickly the magma or lava cools down, you’ll have either smaller or larger crystals.
There are 2 kinds of igneous rocks:
a. Plutonic- intrusive rocks- cool under ground. The magma takes a long time to cool, so there are big crystals. There is 1 exception though- pegmatite has very big crystals because the magma had a lot of water, but it’s not plutonic
b. Volcanic- it’s an extrusive rock- magma is above the ground. It cools quickly so it has small crystals.
Some magma cools so quickly that there are no crystals such as volcanic glass and obsidian.
Sometimes there are gas bubbles in the lava so the rocks are going to form vesicles or air bubbles in the rocks.
We classify igneous rocks according to their crystal size and color- some are light colored and some are dark colored. The color signifies their mineral composition.
Light colored rocks are felsic rocks because they are basically made up of feldspar and silicon. Dark colored rocks are mafic rocks because they are made up of magnesium and ferrum.
2. Sedimentary- formed from the weathered remains of preexistent rocks that are compressed and cemented together. The pieces that sedimentary rocks are usually made up of are rounded by abrasion and deposited in layers. Sometimes there’s a thin layer of sedimentary rocks underground on top of all other kinds of rocks.
a. Clastic/ fragmental- made up of all different size particles. The most common type of sedimentary rocks.
b. Bio clastic- has organic remains. It is rich in fossils:
1. Coal
2. Limestone
c. Crystalline- made up of sediment precipitation. There are chemical reactions in certain liquids that will form precipitates.
3. Metamorphic- form when sedimentary or igneous rocks are changed by intense heat or pressure. Metamorphic rocks never leave the solid state. These are the only rocks that come directly from other rocks.
There are a few things that happen when a rock becomes a metamorphic rock:
a. The layers inside the rock will become distorted or disappear completely.
b. New minerals will form inside the rock.
c. Crystals will begin to grow.
Some metamorphic rocks have foliation- layers have formed inside the rock as the crystals realign themselves. 1 type of foliation- banding- minerals separate into dark and light layers.
2 types of metamorphism that take place:
1. Regional metamorphosis- rocks form deep within the earth. We see these rocks mainly when rocks are pushed up when mountains form. Metamorphic rocks usually form the core of the mountain.
2. Contact metamorphosis- rocks are changed near earth’s surface because of nearby magma and lava. Contact metamorphosis doesn’t change as drastically as regional metamorphosis.

Natural resources- substances that are found within earth, for example metal, minerals, fossil fuels, non-metals…

What are renewable resources? Those that the earth can reproduce, for example trees and water.

Non-renewable resources can’t be recycled or take a long time to reproduce, for example metals aren’t recyclable. Deep in the ocean are stream vents that can create metals but it takes years for metals to reproduce.

Coal and iron are also non-renewable, so we need to find alternate energies:
1. Solar energy- only good for the daytime.
2. Geothermal energy- from the earth. Can only be accessed in certain areas.
3. Wind driven generators- only works in places with strong and steady wind.
4. Hydro- electric power- uses water to create electricity. When they contain a lot of water in 1 area, it caused floods.
5. Nuclear energy- creates tremendous amount of radioactive wastes.