1. UNIT 2: Earth Materials

2. Overview of the Unit Minerals: -definition -formation -types
-identification/tests
Rocks: -definition
-formation and rock cycle
-categories/types
-identification
Materials as a resource
-mining (oral presentation)

3. First… a review of basic chemistry
Atoms are composed of a dense nucleus containing protons and neutrons that is orbited by electrons. The number of protons indicates what element it is.
These electrons orbit in distinct energy levels (shells). Each shell can only have a specific number of electrons before it becomes full and a new shell must be started. The electrons in the outermost shell are called valence electrons.
The number of valence electrons dictate how the elements react. Remember: atoms want full valence shells, either by gaining or losing electrons (ionic bonds), or by sharing electrons (covalent bonds).

4. A closer look at ionic bonds
When a metal and a non-metal bond, the metal will transfer 1 or more electrons to the non-metal so that they both have full valence shells.
The result is that the positive metal ion is attracted not only to the negative non-metal ion it gave its electron(s) to, but also all the other non-metal ions.
This results in a crystal lattice structure.

5. More on crystals...
Not all crystals take this shape. (Only ionic compounds in a 1-1 ratio like NaCl)
Other ionic compounds not in 1-1 ratios (ie. BeCl2) may have different structures.
Even some covalent bonds result in the formation of crystals (diamond, for example, which is just a carbon crystal).

6. Properties of Crystals
The bonds between ions in the same plane are quite strong, but the attraction between planes may not be.
As a result, crystals generally appear to have very distinct shapes.

7. Minerals
Definition: A mineral is a naturally occurring, inorganic, solid element or compound with definite composition and regular internal crystal structure.

8. Classifying Minerals
Surprisingly, using colour to classify or identify a mineral is usually not appropriate.
The reasons for this are
1) Many minerals may have the same colour for different reasons
2) The same mineral may be found in several different colours due to impurities inside the mineral.
Example: Pure corundum is colourless, and is often used as grit in sandpaper. When colour is added we get...
Red --> rubies
Blue --> sapphire

9. Classifying Minerals
Minerals can be classified based on two properties...
1) composition
2) crystal structure
Here are some common groups…

10. Silicates: composed of silicon and oxygen and often other elements
most common minerals (since Si and O are the two most common elements in Earth’s crust)
subdivided based on crystal structure (we won’t go into details here)
Some common examples:
quartz (SiO2) --> used to make glass
also found in some watches
with a purple tint (impurities) it is called amethyst
feldspars --> also contain Al + either Na, K, or Ca
ferromagnesians --> also contain Fe and/or Mg
clays --> sheets of Si and O stacked on each other
weak bonds between sheets, thus slippery
may absorb water and expand

11. Silicates Quartz Feldspar - nepheline (Na, K, Al, Si, O) Amethyst
Clay - talc
(Mg, Si, O, OH)
Ferromagnesian - biotite
(K, Fe, Mg, Al, Si, O, OH, F)

12. Some Non-Silicates Carbonates metals + CO3
most common carbonate is calcium carbonate (CaCO3)
Note: Calcite is a group in the form of XCO3 where X is an element in the same group as Ca.
Sulfates
metals + SO4
Example: gypsum (calcium sulfate with water, CaSO4(2H2O))

13. Some Non-Silicates Sulfides metals + S (no O)
Example: pyrite (fools gold)
Oxides
metals + O
Examples:
corundum (Al2O3)
magnetite (Fe3O4)
hematite (Fe2O3)

14. Some Non-Silicates Hydroxides metals + OH Example: gibbsite (Al(OH)3)
Halides
metals + a halogen
Example: halite (NaCl)
Native Elements
any mineral consisting of a single element
Example: gold