Minerals. Goals 1) To understand what minerals are and how they are put together; 2) To examine some...
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Transcript of Minerals. Goals 1) To understand what minerals are and how they are put together; 2) To examine some...
Minerals
Goals1) To understand what minerals are and how
they are put together; 2) To examine some important ore minerals; and 3) To examine some of the most common rock forming minerals
To earn the name mineral• Naturally occurring and inorganic solid
• Characteristic chemical composition
• Regularly repeating internal crystalline structure
Silicon + 2 oxygen
SiO2
Who has earned the name
• Ice (H2O) is a mineral, liquid water is not: Why?
• Quartz (SiO2) is a mineral, glass is not: Why?
Atoms and atomic bonds
Why are diamonds hard and pencil “leads” (graphite) soft?
Graphite
Diamond
Diamond Saw
Atoms• Nuclease of Protons (+) and Neutrons (0)
• Cloud of orbiting Electrons (-)
Electrons (e-)Electrons are divided into groups called orbitals• Outer orbital of Hydrogen and Helium can hold 2
electrons• Outer orbitals of all other atoms can hold 8 electrons
Orbitals2 e-
8 e-
Chemical bondsAll atoms are greedy little buggers—They all
want a full outer orbital, and they’ll bond with almost anyone to get it!
Chemical bonds allow atoms to exchange or share electrons
Methane: Carbon bonded to four
hydrogen atoms
Ionic bondsOne atom’s trash is another atom’s treasure
Cations: throw away their outer electrons—net positive charge
Anions: pickup cast-off electrons—net negative charge
Salt combines sodium cation
(Na+) with chlorine anion (Cl-)
Covalent bondsAtomic monogamy: Atoms share outer
electrons with a few partners.
Strongest type of bond
In methane carbon shares one outer e- with 4 hydrogen atoms
quartz contains covalent bonds
Metallic bondsAtoms have a giant electron orgy
Nuclei float in a sea of shared electrons
Intermolecular bondsBonded atoms do a little sharing on the side
Weakest type of bond!
Some molecules have a weakly positive side and a weakly negative side
Water
Think-pair-share activity
1. We know that diamonds are one of the hardest substances known to man and graphite is one of the softest. Both are made entirely of carbon
2. Come up with an explanation for this.
3. Compare, discuss, and refine your idea with one or two of your neighbors.
4. Write up your results and pass them in.
DiamondGraphite
Different types of bonds
Crystalline structure• Geometric
arrangement of atoms
• Dictated by the types of elements present and the pressure and temperature conditions
DiamondGraphite
Same chemical composition, different pressure and temp.
Important ore mineralsOre: metal-bearing mineral or rock that can be
mined for a profit
Jet engine—We need iron (steel), titanium, and aluminum... where do we get these metals?
Oxide minerals metal atoms covalently bonded to oxygen
Hematite and magnetite — Iron oxides• Our primary source of iron• Found in banded iron formations (BIF’s)• Most BIF’s 2–3 b.y. old
Rutile — Titanium oxide• One of our main sources of titanium• Often concentrated in beach sands
Bauxite — Aluminum bonded with oxygen and hydrogen (aluminum hydroxide)
• The main source of aluminum• Forms due to extreme weathering in tropical
soils
Iron (steel), titanium, and aluminum in this jet engine come from:
• 2.5 b.y. old rocks deposited in the deep ocean• Beach sand• Tropical soil
No puppies were harmed in the making of this jet engine
Pyrite — Iron sulfide• Common in coal beds and ore deposits• Source of much acid mine drainage
Sulfide minerals metal atoms ionically bonded to sulfur
Chalcopyrite — Copper-iron sulfide• Often found in volcanic rocks found at
convergent margins• Primary source of copper
Rock forming mineralsMinerals that make up most of the earth
Most common elements in the crust
1.Oxygen
2.Silicon
3.Aluminum
4. Iron
5.Calcium
6.Magnesium
7.Sodium
8.Potassium
Silicate mineralsSilicate minerals—built around pyramid-shaped
combinations of silicon and oxygen atoms called silica tetrahedrons
Silica tetrahedron: Silicon atom covalently bonded to 4 oxygen atoms
Silicate minerals fall into two categories:
Mafic minerals—silica tetrahedrons bonded to iron, magnesium, and calcium
Felsic minerals—silica tetrahedrons bonded to aluminum, potassium, and sodium
• Generally dark colored• More dense• Common in oceanic lithosphere
• Generally light colored• Less dense• Common in continental lithosphere
Mafic mineralsOlivine—single silica tetrahedrons covalently
bonded to magnesium or iron• Makes up 90% of the mantle
Mafic mineralsPyroxene—chain of silica tetrahedrons bonded to
magnesium, iron, and calcium
Mafic mineralsAmphibole—double chain of silica tetrahedrons
bonded to magnesium, iron, and calcium
Mafic mineralsBiotite—sheets of silica tetrahedrons bonded to
magnesium, iron, and potassium
Felsic mineralsMuscovite—sheets of silica tetrahedrons bonded
to aluminum and potassium
Felsic mineralsPotassium feldspar—network of silica tetrahedrons
bonded to potassium and aluminum
Felsic mineralsQuartz—network of silica tetrahedrons
Silicon dioxide
Most common mineral in crust
Plagioclase feldspar mineralsPlagioclase feldspars—network of silica
tetrahedrons bonded to calcium (mafic) and/or sodium (felsic)
• Calcium plagioclase feldspar = mafic
• Sodium plagioclase feldspar = felsic
Calcium plagioclase feldspar = black lab
puppy
Sodium plagioclase feldspar = yellow lab
puppy
Potassium feldspar = golden retriever puppy
Sodium+Calcium plagioclase feldspar
= chocolate lab puppy
Mafic
Felsic
Feldspar minerals are like
retriever puppies
Other important mineral groupsClay minerals—Sheet silicates that form due to
chemical alteration at the Earth’s surface• Very common in soils• Used to make paper, ceramics, and bricks
Other important mineral groupsCarbonate minerals—Combine carbonate ions
(CO32-) with calcium to make Calcite and calcium
and magnesium to make dolomite
Extremely important to global carbon dioxide cycles