G119 Lecture: Week 1
What is the difference between a rock and a mineral?
Three basic groups of rocks
Igneous:
Rocks form from magma
Sedimentary:
Rocks form from evaporation
Rocks form as sediments compact
Metamorphic:
Rocks form as heat and/or pressure is applied to pre-exisiting rocks
Seven basic groups of minerals
Halides, Native minerals, Carbonates, Nitrates, Sulfates, Sulfides
These are known as the Ore Minerals
Silicates
These are known as the rock forming minerals
Definition of a Mineral
Inorganic
Naturally occurring
Solid with an organized crystal structure
Known chemical composition
Where do minerals form?
Minerals form from magma
Minerals form by evaporation
Minerals can change to new minerals through heat and pressure
Why should we care about minerals?
Copper: Wire and piping
Gypsum: Wallboard
Sulfur: Medicinal
Talc: Cosmetics/powder paint
Halite: Salt
Diamonds: Cutting tools
Minerals help us understand rocks
Recognize the type of rock based on the minerals we see
Minerals help us understand about conditions of formation
Every mineral has a temperature and pressure regime in which it is stable.
We can recognize what physical conditions the rock formed under based on the minerals we see
Polymorphs
Two or more minerals that have the same chemistry but different crystal structures
Caused by difference in heat and pressure
How do minerals form?
Chemical elements bond together in different ways (more next week)
How they bond depends on the elements present and the environment
Mineral growth
Two stages of mineral growth:
Nucleation
Formation of the nucleus of the mineral
Requires LARGE amounts of energy
Growth
Minerals grow as atoms add to outside edges of the nuclei
Only occurs when conditions are good
Change in environment can determine how a mineral will grow
Pseudomorphs
When conditions change and a mineral is converted into a different mineral but retains its crystal structure or shape
How do we tell one mineral apart from another?
Mineral Properties
Color
Hardness
Streak
Habit
Luster
Density
Taste/smell
Magnetism
Chemical reactivity
Cleavage/Fracture
Different properties are due to the chemical make up and bonding of minerals.
We can tell one mineral from another by:
their properties
Quartz hardness 7
vs Fluorite hardness 4
Rocks we find them in
Associated minerals
Hardness
Measured with Mohs hardness scale
Scale rated 1-10
Streak
Based on what color the mineral is when it is powdered. Not necessarily the same as
the color of the mineral itself
Use a streak plate to determine
Habit
This is the common shape or crystal structure a mineral will have
Not necessarily unique but with other properties can help identify the minerals
Luster
Metallic
Shine
Opaque
Rusty?
Non metallic
Earthy
Pearly
Waxy
Adamantine
Glassy
oily
Density
Measures as grams per cubic centimeter
Galena: 7.4-7.6 g/cm3
Sulfur: 2.05-2.09 g/cm3
Approximate with heft test
or
Measure with mass and water displacement
Fracture or Cleavage
Taste, smell, chemical reactivity and magnetism
Halite (salt)
Kaolinite (clay)
Calcite
magnetite
COLOR?
HOMEWORK:
What is Bauxite?
What type of environment does it form in?
What is it made of?
Why is it important?
Where in the USA is it found?