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