Rocks & Minerals

Element Quiz: Give the Symbol
1.
2.
3.
4.
5.
Oxygen
Hydrogen
Iron
Potassium
Silicon
6. Aluminum
7. Calcium
8. Sodium
9. Carbon
10. Magnesium

1.
2.
3.
4.
5.
O
H
Fe
K
Si
Answers to the Quiz
6. Al
7. Ca
8. Na
9. C
10. Mg

What is a Mineral?





Naturally Occurring
Inorganic
Solid
Definite Chemical Formula
Definite Crystal Structure

Naturally Occurring



Formed by natural processes not in the laboratory.
Minerals are inorganic- are not alive
Example


Salt is a mineral
Sugar is not – it was harvested from plants

Bling Bling


Diamond is a mineral
Cubic zirconia is NOT

Definite Crystal Structure

Highly ordered atomic arrangement of atoms in regular geometric patterns
Apatite Feldspar Diamond
8
Quartz

Definite Chemical Formula

Minerals are expressed by a specific chemical formula
-Gold (Au)
-Calcite (CaCO
3
)
-Quartz (SiO
2
)
-Pyrite (FeS
2
)

Composition of the Earth’s Crust
 Eight Elements that make up over 98% of Earth’s Crust
-Oxygen (O)
-Silicon (SI)
-Aluminum (Al)
-Iron (Fe)
-Calcium (Ca)
-Sodium (Na)
-Potassium (K)
-Magnesium (Mg)

Where Do Minerals Come
From?

Precipitation

Crystallization of Magma

Pressure and Temperature

Hydrothermal Solutions

Precipitation
Earth water sources contain dissolved substances which can react to form minerals
Evaporation

Crystallization from Magma
As magma cools elements combine to form minerals
Magma

Temperature and Pressure

Form when existing minerals are subject to changes in temperature and pressure

Hydrothermal Solutions

When very hot water and substances come in contact with one another reactions occur and minerals can form

How Are Minerals Identified?








Color
Luster
Hardness
Streak
Density
Crystal Shape
Cleavage and Fracture
Special Properties

Color

Usually the first and most easily observed
-Some minerals are always the same color
-Some minerals can have many colors
ROSE QUARTZ QUARTZ SMOKY QUARTZ

Luster

General appearance of a mineral surface in reflected light
GlassyObsidian


Hardness
Resistance to scratching by different items; “scratchability”
Mohs Hardness Scale
>2 fingernail
3 penny
~5 Steel of a pocket knife
5.5 Window Glass
6.6 Steel of a file
7 quartz crystal

Mohs Mineral Hardness Scale
1) Talc
2) Gypsum
3) Calcite
4) Flourite
5) Apatite
6) Feldspar
7) Quartz
8) Topaz
9) Corundum
10) Diamond
Softest
Hardest
1
2
3
5
6
7
4 8
9
10

Streak


The color of a finely powdered mineral
Determined by rubbing the mineral on a piece of unglazed porcelain (streak plate)

Density

The amount of matter in a given space
(Mass/Volume)

Crystal Shape

Minerals have a characteristic crystal shape resulting from the atomic packing of the atoms when the mineral is forming

Cleavage and Fracture


Cleavage is the tendency of a mineral to split or crack along parallel or flat planes
Fracture occurs when a mineral breaks at random lines instead of at consistent cleavage planes.
BIOTITE QUARTZ
Obsidian
1 Direction of Cleavage No Cleavage Conchoidal Fracture

Special Properties





Magnetism (Magnetite)
Glowing under ultraviolet light (Fluorite)
Salty taste (Halite)
Smell (Sulfur)
Reaction to HCl (Calcite)
Magnetite

Economic Importance of Minerals

Minerals are in many things we see and use everyday such as; bricks, glass, cement, plaster, iron, gold

Every American Requires 40,000
Pounds of New Minerals per Year
 at this level of consumption the average newborn infant will need a lifetime supply of:
-795 lbs of lead (car batteries, electric components)
-757 lbs of zinc (to make brass, rubber, paints)
-1500lbs of copper (electrical motors, wirings
-3593 lbs aluminum (soda cans, aircraft)
-32,700 lbs of iron (kitchen utensils, automobiles, buildings)
-28,213 lbs of salt (cooking, detergents)
-1,238,101 lbs of stone, sand, gravel, cement (roads, homes, etc.)

Minerals Pop Quiz
2
3
4
1
What are two characteristics of a mineral?
Define Luster.
What is one way minerals form?
Why is color not the best way to identify a mineral?