1. MINERALS

2. What is a mineral?
Naturally occurring, inorganic solid with an orderly crystalline structure and chemical composition
1. Naturally occurring = by natural geologic processes (ex: cooling of feldspars in magma) not man made; cubic zirconium)
2. Solid
3. Orderly, repetitive structure (in terms of arrangement of atoms; Opal or glass are not minerals for this reason).
4. Definite chemical composition (represented by chemical formulas like SiO2 )
5. Generally inorganic (not produced from living things; CaCO3 = calcium carbonate or Calcite is an exception; makes up shells of marine animals).

3. Mineral Formation
1. Crystallization from magma - Iron, magnesium, and calcium minerals 1st; then sodium, potassium, quartz minerals
2. Precipitation of solid mineral when water evaporates out.
3. Pressure and temperature - cause metamorphism = changes in pressure and temperature that allow minerals to migrate and react with each other in new ways --> form new minerals.
4. Hydrothermal Solutions - Hot mixture of dissolved substances

4. Physical Properties of Minerals
- depends on chemical composition and crystal composition
Color
Streak
Luster
Crystal Form
Cleavage/Fracture
Density
Hardness

5. Color: Helpful, but not nec
Color: Helpful, but not nec. diagnostic; some minerals have a colored varieties
Corundum’s structure is the same. Trace amounts of different element produce a variety of colors.
Red = Ruby; Blue = Sapphire

6. Streak: color of mineral in powdered form
Tested by…
Streak plate – rub mineral across white tile.
hematite
Streak not nec. Same as color.
only useful for metallic minerals

7. Luster = How mineral’s surface reflects light
Metallic Luster
(= like metal)
Galena
Pyrite
Non-Metallic Luster: (Vitreous = like glass)
Halite & Quartz

9. Crystal Form: How atoms are arranged internally
Platy minerals = flat like sheets (ex. Muscovite)
Hexagonal = quartz
Calcite = rhomboid
Galina = cubes
Diamond (C)
Graphite (C)

10. Hardness: Resistance to being scratched
Can be scratched by glass, but not penny = Moh’s hardness of 4-6

11. Cleavage & Fracture: tendency of a mineral to break along flat, even surfaces
Cleavage: Minerals break along the planes of their weak bonds.
Perfect Cleavage = Micas (muscovite & biotite) = cleave along 1 plane.
Results = sheets
Halite = 2 cleavage planes
Fracture: uneven breaking of mineral surface; conchoidal
- no cleavage pattern

12. Cleavage

13. - will fizz in calcium minerals.
Reaction w/ acid
- will fizz in calcium minerals.
Calcite (CaCO3) = vigorous reaction on all surfaces
Dolomite (Ca,Mg)CO3= mild reaction on powder; scratch then add acid

14. Density = mass/volume (gm/cm3; typical range 2 to 8 gm/cm3)
Magnetism (magnetite) – Contains iron
Flourescence = Minerals give off wavelengths in U.V.