MINERALS

u ROCK
- An aggregate of MINERALS (usually)
u MINERAL
- Crystalline- orderly arrangement of atoms
- Naturally occurring
- Inorganic
- Definite chemical composition
t e.g. SiO2 for quartz; KAlSi3O8 for feldspar
u Chemical composition of the Crust (composition of the average rock
u The most common minerals will be composed mostly of these elements
u Know the three most abundant elements, which are:
u Most abundant elements
- Oxygen O
- Silicon Si
- Aluminum Al
u Silicates
- Most common minerals
- Si + O
- Silica (silicon + oxygen) tetrahedron
t The basic building block
Most Common Minerals
u FELDSPAR- Si + O + Al + …
- Most abundant mineral group
u QUARTZ- SiO2
u "Ferromagnesian" Minerals
- A number of minerals.
- All contain Si + O + Fe & Mg
u MICA- Si + O in sheets (& Al)
u CALCITE- CaCO3
Properties of Minerals
u Color
- not always reliable
- "ferromagnesians" usually green or black
u Luster
- Metallic
- Nonmetallic
t glassy (most common)
t earth or dull
u Hardness
- relative scratchability
- Mohs' hardness scale- 1-10
t fingernail 2.5
t glass or knife blade 5.5
u Crystal form-
- flat outer faces
- angles between faces constant for a particular mineral
u CLEAVAGE
- breakage along flat, parallel planes
- controlled by planes of weakness in the crystal structure
- quality of cleavage (e.g. "excellent")
- Mica- 1 direction, excellent
- Feldspar- 2 directions at right angles, good
- Calcite- 3 directions, not at right angles, excellent
u Fracture
- Absence of cleavage
u Some unusual properties
- magnetism
- taste
ROCK CYCLE
u Interrelationships between
- igneous rocks
- sedimentary rocks
- metamorphic rocks
- weathering and erosion