1. Minerals
This is not a spider web. It is a fractal; a repeating geometric design

2. What is a mineral A mineral is a natural, inorganic, crystalline solid
Ask these questions:
Is it organic? (is it alive or was it once alive)
Coal is made from dead plants and is organic
Does it occur naturally ?
Steel is man-made and is not a mineral
Does it have a crystalline form?
Petroleum occurs naturally and is inorganic but is not a solid so it has no crystalline form and is not a mineral
Does it have a definite chemical composition?
Mixtures are not minerals; compounds can be minerals

3. Types of Minerals The most common minerals are rock-forming
All minerals fall into two categories:
Silicate minerals
Non-silicate minerals

4. Silicate Minerals
All silicate minerals contain silicon (Si) and Oxygen (O) in varying combinations
Quartz contains only Si and O
Feldspar is the most common silicate mineral
Different types of Feldspar are formed when other elements (K, Na, Ca, etc) are combined with the Si and O
Feldspar and quartz make up 50% of the earth’s crust
Silicate minerals make up 96% of the Earth’s crust

5. Non-silicate Minerals
Only 4% of the Earth’s crust
6 groups:
Sulfides
Sulfates
Oxides
Halides
Carbonates
Native Elements

6. Crystalline structure
A crystal is a natural solid with a definite shape
A large mineral crystal will display the characteristic geometry of its crystalline structure
Crystals have a specific geometry of atoms that repeats (like a trelis)
If a mineral is allowed to develop unrestricted then it will form one, huge crystal

7. Crystal Shapes
Draw table 9.3

8. Mineral identification
A Mineralogist is a scientist who identifies minerals
Characteristics:
Color
Luster
Streak
Cleavage/fracture
Hardness
Crystal shape
Density

9. Color
This is probably the worst characteristic to classify minerals because it is inconsistent
Some minerals have distinctive colors (Sulfur is yellow, azurite is blue, serpentine is green)
Many minerals are similar in color
Very small amounts of certain element can greatly affect the color
Corundum is a colorless mineral made from Aluminum and Oxygen but with a little bit of chromium it forms a ruby
Sapphire is corundum with traces of cobalt and titanium
Amethyst is quartz that has a purple color because of small amount of Manganese and Iron

10. Luster Light reflected off the surface of a mineral is called luster
Minerals will either have metallic luster (shiny) or nonmetallic luster (not as shiny)
Minerals that have no shine have a dull, Earthy luster

11. Streak
The color of the mineral in its powdered form is called the streak
This is fairly reliable for identification
Metallic minerals have a dark streak
Ex. Pyrite (fool’s gold) has a black streak
Nonmetallic minerals have a streak that is colorless or a very light shade of the mineral’s normal color

12. Cleavage and Fracture
Cleavage: when a mineral splits evenly along flat surfaces
Ex. Micas which split in sheets
The cleavage runs parallel to a plane in the crystal where the bonding is weak
Fracture: when a mineral breaks unevenly
Curved surfaces are called conchoidal
Fibrous surfaces look like broken wood
Rough surfaces are called uneven or irregular

13. Hardness Hardness is the ability of a mineral to resist scratching
Ex. A diamond is extremely hard but can easily be split along cleavage planes
The hardness of an unknown mineral can be determined by scratching it against other minerals of a known hardness on the Mohs hardness scale
The hardness of the mineral determines the strength of the bonds between the atoms
Graphite and diamonds are made from carbon. Graphite has no crystal structure so it is not as hard as diamonds

14. Crystal Shape
A certain mineral always has the same general shape because the atoms or ions that form its crystals always combine in the same geometric pattern

15. Density Density = Mass ÷ Volume
The density depends on what type of atoms the mineral contains and how closely they are packed together
Most of the common minerals have densities between 2 and 3 g/cm3
Heavy metals (gold, uranium, lead) can have densities from 7 to 20 g/cm3

16. Special Properties Magnetism Double Refraction Radioactivity
Magnetite is the most common
Lodestone is a type of magnetite that acts like a magnet
Double Refraction
Clear minerals still fracture light that passes through them creating double images
Radioactivity
Some atoms have unstable protons and neutrons. This nuclear decay releases energy
Uranium and Radium are some radioactive elements that occur in minerals
Pitchblende is the most common uranium containing mineral

17. Special Properties Florescence (ability to glow under UV light)
Calcite is white under normal light but red under UV light
Florescent minerals absorb UV light and then produce visible light of various colors
Phosphorescence (ability to glow under UV light even after UV light is shut off)