1. Earth’s Materials and Processes-Part 6 Minerals

2. Minerals Naturally occurring, solid, crystalline substance.
Generally inorganic.
Has a specific chemical composition.
Arranged in a repeating 3-D array (crystalline)
Building Blocks of Rock

3. Atomic Structure
Ionic Bonds: electrical attraction between ions of opposite charge.
Strength increases with the electrical charges of ions.
Bond strength decreases as distance between bonds increases.
Most minerals contain ionic bonds.
Ex: Halite (NaCl)

4. Atomic Structure Covalent Bonds Electrons are Shared
Generally stronger than ionic bonds.

5. Crystallization of Minerals
Need a starting material with atoms that can come together in the proper proportions.
Ex: Growth from a liquid or a gas.
Time and space for crystallization.
Appropriate temperature and pressure.
Examples:
Magma that has cooled.
Supersaturated solution  precipitation reaction.
Crystal begins as an initial, microscopic crystal.
Atoms continue to be added in a 3-D array, repeating in the basic arrangement.
Crystal faces are based on the array structure.

6. Cations and Anions
Cations (positively charged) ions are typically relatively small.
Anions (negatively charged) ions are typically large.
Crystal structure is determined largely by the arrangement of cations and of the anions.

7. Compound Ions Many common minerals are silicates.
Complex ions act as a single ion in forming a crystal structure.
Example: Silicate Ions (SiO44-)

8. Cation Substitution Crystal structure determined by large cations.
Cations can substitute for each other in other minerals.
Same crystal structure
Different chemical composition
Polymorphs:
Minerals with the same composition, but different chemical structure.

9. Example

10. Common Rock-Forming Minerals

11. Silicates Most abundant mineral in Earth’s crust.
Silicate ion (SiO44-)
Includes: Quartz, K-Feldspar, Olivine

12. Carbonate Cations with carbonate ions (CO32-)
Calcite, Dolomite, Siderite, Smithsonite.
Make up many common rocks including limestone and marble.

13. Oxides Compounds of metallic cations and oxygen.
Important for many metal ores needed to make things (iron, chromium, titanium)
Economically Useful (possible to mine)

14. Sulfides Metallic cations with sulfide (S2-) ion
Important for ores of copper, zinc, nickel, lead, iron.
Examples: Pyrite, Galena,

15. Sulfates
Minerals with sulfate ion (SO42-)
Example: Gypsum

16. Identification of Minerals
Chemical composition
Crystal Structure
Physical Properties
Hardness

17. Mohs Scale
Used to measure mineral hardness.

18. Physical Properties
Cleavage: tendency of minerals to break along flat, planar surfaces into geometries that are determined by their crystal structure.
Fracture: Tendency to break along other surfaces (not cleavage planes).
Luster (metallic, earthy, etc.)
Color (often a poor indicator, streak color is better).
Specific gravity
Crystal habit (shape).