Earth Science NotesEarth Science Notes

MINERALSMINERALS

Definition of a MineralDefinition of a Mineral

A mineral is a A mineral is a naturally occurringnaturally occurring, , inorganic, homogeneous solidinorganic, homogeneous solid with a with a definite definite chemical compositionchemical composition and an and an ordered atomic ordered atomic arrangement.arrangement.

Five parts to this definition Five parts to this definition

Naturally occurringNaturally occurring – not man made, may be – not man made, may be found on earth, space, or other planets.found on earth, space, or other planets.

InorganicInorganic – minerals are not formed by living – minerals are not formed by living things but by earth processes.things but by earth processes.

Five parts to this definitionFive parts to this definition

Homogeneous solidHomogeneous solid – made up with the same – made up with the same atoms throughout the mineral.atoms throughout the mineral.

The Mineral Halite (Sodium Chloride)

Five parts to this definitionFive parts to this definition

Definite chemical compositionDefinite chemical composition - atoms must - atoms must occur in the same ratios.occur in the same ratios.

Most minerals are Most minerals are ionic compoundsionic compounds – recall ionic – recall ionic compounds have a definite ratio of atoms compounds have a definite ratio of atoms aluminum oxidealuminum oxide 2:3 ratio 2:3 ratio

(2 Aluminum atoms to 3 Oxygen atoms)(2 Aluminum atoms to 3 Oxygen atoms)

Five parts to this definitionFive parts to this definition

Ordered atomic arrangementOrdered atomic arrangement – must be – must be crystallinecrystalline – have repeating units – have repeating units Unit cellUnit cell – the most basic component of a crystal. – the most basic component of a crystal.

Glasses, like obsidian, are not mineralsGlasses, like obsidian, are not minerals

Orderly Atomic Arrangement Orderly Atomic Arrangement

Crystals: solids where atoms are arranged in an orderly repeating pattern.

Front View of Crystal Lattice Enlarged 3-D view of Unit Cell

Orderly Atomic ArrangementOrderly Atomic Arrangement

Crystal LatticesCrystal Lattices – repeated unit cells – repeated unit cells

Orderly Atomic ArrangementOrderly Atomic Arrangement

Crystal SystemsCrystal Systems – made up of crystal lattices – made up of crystal lattices Types of crystal systems (also see p 64)Types of crystal systems (also see p 64)

CubicCubic HexagonalHexagonal Monoclinic Monoclinic TetragonalTetragonal Orthorhombic Orthorhombic

TriclinicTriclinic

Orderly Atomic ArrangementOrderly Atomic Arrangement

Unit Cell Unit Cell Crystal Lattice Crystal Lattice Crystal System Crystal System

Mineral FormationMineral Formation

Minerals form as a result of two processesMinerals form as a result of two processesMagma coolingMagma cooling Minerals formed depend on the elements present and Minerals formed depend on the elements present and

the amount of those elements.the amount of those elements. The size of the mineral crystal depends on the rate at The size of the mineral crystal depends on the rate at

which the crystal cooled.which the crystal cooled.

Mineral FormationMineral FormationMinerals form as a result of Minerals form as a result of two processestwo processesSolutions evaporatingSolutions evaporating Solutions have two partsSolutions have two parts

SoluteSolute – substance being dissolved – substance being dissolved SolventSolvent – substance doing the dissolving – substance doing the dissolving

With some solutions the solvent (water) can be With some solutions the solvent (water) can be evaporated and the solute (salt) dissolved evaporated and the solute (salt) dissolved reappears in crystal form.reappears in crystal form.

Mineral FormationMineral Formation

Solutions evaporating to form minerals: Solutions evaporating to form minerals: the spotted the spotted lake (kliluk), situated in osoyoos, Canada, contains one of the highest lake (kliluk), situated in osoyoos, Canada, contains one of the highest concentrations of minerals in the world (mainly epsom salts, calcium concentrations of minerals in the world (mainly epsom salts, calcium and sodium sulphates). and sodium sulphates).

Mineral ClassificationMineral Classification

Most mineral groups are based on the elements that Most mineral groups are based on the elements that are in the mineral.are in the mineral. SilicatesSilicates – vast majority of the earth’s crust. – vast majority of the earth’s crust.

Ex: Quartz and Feldspar Ex: Quartz and Feldspar Oxides Oxides – minerals that have oxygen in them.– minerals that have oxygen in them.

Ex: Hematite and Magnetite Ex: Hematite and Magnetite SulfidesSulfides – minerals that have sulfur in them. – minerals that have sulfur in them.

Ex: Pyrite and galena Ex: Pyrite and galena HalideHalide – … have one of the halogens in them. – … have one of the halogens in them.

Ex: halite (NaCl) and FluoriteEx: halite (NaCl) and Fluorite Pure metal elementsPure metal elements: Gold, silver, etc: Gold, silver, etc

Mineral IdentificationMineral Identification

Physical PropertiesPhysical Properties of minerals allow for of minerals allow for accurate identification accurate identification

HardnessHardness LusterLuster Specific GravitySpecific Gravity StreakStreak Cleavage Cleavage Special Properties Special Properties

Mineral IdentificationMineral Identification

HardnessHardness: : determine by determine by Mohs ScaleMohs Scale

HARDNESS SCALE

INDEX MINERA

L

COMMON OBJECTS

1 Talc

2 Gypsum Fingernail

3 Calcite

4 Fluorite Copper Penny

5 Apatite

6 Orthoclase

7 Quartz Glass

8 Topaz

9 Corundum

10 Diamond

Mineral IdentificationMineral Identification

LusterLuster: reflecting of light: reflecting of light The two main types of luster are The two main types of luster are metallicmetallic and and

nonmetallicnonmetallic. .

Metallic luster Nonmetallic Luster

Mineral IdentificationMineral Identification

Specific GravitySpecific Gravity: Specific gravity is the : Specific gravity is the "heaviness" of a mineral. "heaviness" of a mineral. It is defined as a number that expresses the ratio It is defined as a number that expresses the ratio

between the weight of a mineral and the weight of between the weight of a mineral and the weight of an equal volume of water. Water has a specific an equal volume of water. Water has a specific gravity of 1. gravity of 1.

Mineral IdentificationMineral Identification

StreakStreak: is the color of the powder left on a : is the color of the powder left on a streak plate streak plate

Mineral IdentificationMineral Identification

CleavageCleavage: is the ability of a mineral to break : is the ability of a mineral to break along preferred planes. along preferred planes.

Fracture: tendency of a mineral to break along curved surfaces without a definite shape

Mineral IdentificationMineral Identification

Special Properties of mineralsSpecial Properties of minerals TransparencyTransparency Magnetism Magnetism Tenacity (how tough a mineral is)Tenacity (how tough a mineral is)

Minerals Minerals

Summary Summary What makes something a mineral?What makes something a mineral?

Five characteristics Five characteristics Arrangement and organization of crystal structuresArrangement and organization of crystal structures

Unit Cell Unit Cell lattices lattices Crystal systems Crystal systems Formation of MineralsFormation of Minerals

From lava / SolutionsFrom lava / Solutions Mineral IdentificationMineral Identification

Based on physical propertiesBased on physical properties