sheep creek canyon in the uinta mountains, utah

Sheep Creek Canyon in the Uinta mountains, Utah

The Supercontinent Rodinia existed from ~1 billion years ago to 750 million years ago.

Rodinia is older than Pangea. Pangea existed around 200-300 million years ago.

The 750 million year old sandstones in the Uinta Mountains were deposited at a plate boundary that was undergoing “continental plate separation”.

This is when the supercontinent Rodinia started to break apart.

Make sure to read chapter 3: Plate Tectonics

Next Topic: Minerals - Read chapter 4.

Minerals

Rocks are made of minerals

amphibole

biotite

muscovite

Rocks are made of minerals

Microscopic image of a rock. These pieces are all different minerals.

Feldspar and quartz mineral grains make up a rock called an “arkose”

Definition of a mineral

1. It must be naturally occurring (not human-made)

Naturally occurring specimen

Mineral Name: Corundum

Gem name: Sapphire

Specimen created in the lab

Mineral Name: None (technically, it is not a mineral)

Gem name: Sapphire

Diamond Anvil Cell – produces very high pressures at the diamond tips

Definition of a mineral

2. It must be a crystalline solid

“crystalline” means that the atoms are arranged in an ordered, crystal lattice

An example of a solid that is not crystalline is glass.

A glass is formed by cooling a liquid so quickly that its atoms do not have time to form a lattice.

Opal does not have a crystalline lattice. Therefore, it is not a mineral. It is referred to as a “mineraloid”.

Mineraloid – a mineral-like substance in which the atoms are not arranged in a crystalline lattice.

Definition of a mineral

3. It must be inorganic

“inorganic” means the same as “not organic”

In other words, a mineral CANNOT be created by biological processes.

There is one exception to this rule – the mineral calcite.

Calcite (CaCO3)

The mineral “calcite” is the only exception to this rule. It is often formed organically by sea creatures.

Definition of a mineral

4. It must have a specific chemical composition

Examples:

Halite (table salt) NaCl

Quartz SiO2

Calcite CaCO3

Definition of a mineral

4. It must have a specific chemical composition

3. It must be inorganic

2. It must be a crystalline solid

1. It must be naturally occurring (not human-made)

Is coal a mineral?

Definition of a mineral

4. It must have a specific chemical composition

3. It must be inorganic

2. It must be a crystalline solid

1. It must be naturally occurring (not human-made)

Is ice a mineral?

Definition of a mineral

4. It must have a specific chemical composition

3. It must be inorganic

2. It must be a crystalline solid

1. It must be naturally occurring (not human-made)

Crystal lattice of ice

Before we continue with minerals, we will have a brief refresher on atoms, ions, and bonding.

Atom: the smallest unit of an element that retains the physical and chemical properties of that element

The atomic nucleus is made of protons (positive charge) and neutrons (no charge). The nucleus is surrounded by electrons.

Atomic Number: The number of protons in the nucleus

A carbon atom has 6 protons in its nucleus.

Elements in the periodic table are organized by atomic number (number of protons)

Atomic Mass Number: Number of protons and neutrons

We ignore electrons when calculating the mass number because electrons are so tiny and light compared to protons and neutrons.

Atomic Mass Number: Number of protons and neutrons

Isotopes: Atoms of the same atomic number that have different numbers of neutrons.

Atomic Number: The number of protons in the nucleus

For example, the element Oxygen:

Oxygen has 8 protons, so its atomic number is 8

There are many isotopes of oxygen:

Common examples are: oxygen-16, oxygen-17, and oxygen-18

Oxygen-16 has 8 protons and 8 neutrons (its atomic mass number is 16).

Oxygen-17 has 8 protons and 9 neutrons (its atomic mass number is 17).

Oxygen-18 has 8 protons and 10 neutrons (its atomic mass number is 18).

An Ion is an atom in which the total number of electrons is not equal to the number of protons.

As a result, ions have an electrical charge.

A proton has a +1 charge.

An electron has a -1 charge.

Anion: An atom that has more electrons than protons – the result is a negative charge.

Cation: An atom that has less electrons than protons – the result is a positive charge.

An example is NaCl (salt)

Na has 11 protons and 11 electrons

Cl has 17 protons and 17 electrons

The Na atom can easily lose an electron, so it now has 11 protons and 10 electrons, giving it a +1 charge. It is now an Na cation.

The Cl atom can easily gain an electron, so it now has 17 protons and 18 electrons, giving it a -1 charge. It is now a Cl anion.

Because Na has +1 charge and Cl has -1 charge, they can be electrically attracted to each other.

The main types of molecular bonds in minerals

1. Ionic bonds

2. Covalent bonds

There are others, but these are not as strong (metallic bonds, intermolecular bonds)

Ionic Bonding

Cation (+)

Anion (-)

• Ions of opposite charge are attracted to each other.

• Ionic bonding is the most common bonding in minerals

NaCl is an example of a mineral that is ionically bonded. The name of this mineral is halite. It is commonly referred to as table salt.

Covalent Bonding• Atoms share electrons• Covalent bonding is stronger than ionic bonding

Diamond

Diamond is a mineral that is covalently bonded. It is the hardest natural mineral because it has very strong covalent bonds.

UE4E UE4E Figure 3.11Figure 3.11

Polymorphs have the same formula, but can have very different properties.Polymorphs have the same formula, but can have very different properties.

Carbon and Graphite are good examples of polymorphs – they are both made Carbon and Graphite are good examples of polymorphs – they are both made of carbon.of carbon.

Polymorph: a mineral which has the same chemical composition as another mineral, however, their atoms are arranged differently.

Major classes of rock-forming minerals

Sulfide anion (S2-)Sulfides

Sulfate anion (SO42-)Sulfates

Oxygen anion (O2-)Oxides

Carbonate anion(CO32-)Carbonates

Silicate anion (SiO44-)Silicates

Defining anionClass

(make sure to know these major classes and the anions associated with them)

A mineral class is defined by the anion

For example, these are all carbonate minerals that have the carbonate anion (CO3

2-) in common.

Calcite CaCO3

Siderite FeCO3

Malachite Cu2CO3(OH)2

The only one you need to remember is Calcite.

Silicate minerals are important in geology because most rocks are made of them!

Silicate minerals are those which have the silica anion (SiO44-)

The silica anion is also commonly called the silica tetrahedron because it forms a 4-sided shape with oxygen on the corners and silicon inside.

(by the way, the word “tetrahedra” is the plural of tetrahedron)

Oxygen

Oxygen

Oxygen

The Silica Tetrahedron

Silica tetrahedra can bond together by sharing their corner oxygen atoms