Geology Unit 1

Definition of mineral

A naturally occurring solid with a highly ordered atomic arrangement and definite chemical composition

Definition of mineraloid

A solid that has a similar chemical composition as a mineral, but does not meet all of the criteria to be one

Neutral atoms vs Ions

Neutral atoms have no charge while ions have a positive or negative charge due to losing an electron

Types of ions

Cations are ions that have lost and electron and are positively charged, anions are ions that have gained an electron and are negatively charged

Covalent bond

Covalent bonds are when two atoms share electrons, and the bond cannot be easily broken by water - electron shells overlap (e.g. diamonds and Cl₂)

Ionic bond

Ionic bonds are when an anion gives an electron to a cation, and are the weakest type of bonds - electrostatic attraction (e.g. NaCl)

Metallic bond

Metallic bonds are when metal atoms share electrons freely throughout the crystal structure, allowing heat and electricity to be easily transmitted

Define polymorphs

Polymorphs are molecules that have the same chemical makeup but a differing crystal structure, giving each one a unique properties (e.g. diamonds and graphite)

Define cleavage

The tendency of a substance to break along certain planes due to weak bonds in that area

Why crystals form spontaneously

To lower their overall energy state - Forming crystals allows atoms to satisfy bonds from all sides, allowing them to reach their lowest possible energy state

Steps for crystal formation

1. The formation of the submicroscopic crystal seed as ions bond to each other

2. More bonds form from the seed, growing the crystal as atoms diffuse towards the nucleus

Classes of minerals

Native elements, sulfides (S2-), Oxides (O2-), Carbonates (CO3)2-, and Phosphates (PO4)3-

Most important mineral class and what they are made of

silicates, which are made up of Silicon and Oxygen

First and second most abundant elements in earth’s crust

Silicon and oxygen

How silicate minerals develop (two ways)

Silicate minerals develop through adding positively charged ions to the crystal structure or sharing oxygen between tetrahedrons

Intrusive igneous rocks (where and how they form, what types of rocks they form, how they look

Forms when magma gets trapped underground through very slow cooling, forms many visible crystals, and can become exposed through erosion (e.g. granite)

Extrusive igneous rocks (where and how they form, what types of rocks they form, how they look)

Forms above ground through the rapid cooling of lava, can form volcanic glass (e.g. basalt, obsidian)

Three types of igneous rocks and what they consist of

Mafic (high in Mg and Fe- rich silicates, dark colored), intermediate, Felsic (high in feldspars and SiO2 or silica)

Most abundant igneous rock

Basalt

How basaltic magma is produced

Basaltic magma is produced due to the partial melting of the mantle

How granitic magma is produced

Granitic magma is produced due to the partial melting of the deep crust

How diamonds are brought to the surface

Diamonds are brought to the surface through partial melting of the deep mantle

What is a Dike

A tabular intrusion that cuts across different layers of rock; occurs when magma is injected into a crack

What is a Sill

A tabular intrusion spread through a layer of rock

What is a Batholith

A very large intrusion that cuts along older rocks

What is viscosity

Viscosity is the resistance of a liquid to flow; Water has low viscosity, honey has a very high viscoity

Basalt lava

Low viscosity, forms thin, laterally extensive sheets; very dangerous for humans

Andesite lava

Intermediate in viscosity and flow

Rhyolite lava

High viscosity, forms short, thick flows; not as dangerous for humans

Shield volcanoes

Formed by basalt lava because of its low viscosity, creating a large volcano with gentle slopes; typically nonexplosive

How andesite and rhyolite magmas erupt

Andesite and Rhyolite magmas erupt explosively due to the release of dissolved gases

How do explosions happen

Magma has dissolved gases held in due to high pressure; eruptions happen when gases come out of the solution, lowering pressure and allowing magma to rise

Pyroclasts

Pieces of magma that are broken apart

Volcanic ash

Fine ground pyroclasts less than 2 mm across