1. Earth Science Notes
MINERALS

2. Objectives
I can…
Identify and describe the criteria for crystals classification
Explain the concept of the Unit Cell and tell why it is necessary in explaining mineral structures
Determine the identity of minerals based ont their properties.

3. Definition of a Mineral
A mineral is
naturally occurring,
inorganic,
homogeneous solid with a definite chemical composition
Has ordered atomic arrangement.

4. Five parts to this definition
Naturally occurring – not man made, may be found on earth, space, or other planets.
Inorganic – minerals are not formed by living things but by earth processes.

5. Five parts to this definition
Homogeneous solid – made up with the same atoms throughout the mineral.
The Mineral Halite (Sodium Chloride)

6. Five parts to this definition
Definite chemical composition - atoms must occur in the same ratios.
Most minerals are ionic compounds – recall ionic compounds have a definite ratio of atoms  aluminum oxide 2:3 ratio
(2 Aluminum atoms to 3 Oxygen atoms)

7. Five parts to this definition
Ordered atomic arrangement – must be crystalline – have repeating units
Unit cell – the most basic component of a crystal.
Glasses, like obsidian, are not minerals

8. 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

9. Orderly Atomic Arrangement
Crystal Lattices – repeated unit cells

10. Orderly Atomic Arrangement
Crystal Systems – made up of crystal lattices
Types of crystal systems (also see p 64)
Cubic
Hexagonal
Monoclinic
Tetragonal
Orthorhombic
Triclinic

11. Orderly Atomic Arrangement
Unit Cell  Crystal Lattice  Crystal System

12. Mineral Formation Minerals form as a result of two processes
Magma cooling
Minerals formed depend on the elements present and the amount of those elements.
The size of the mineral crystal depends on the rate at which the crystal cooled.

13. Mineral Formation Minerals form as a result of two processes
Solutions evaporating
Solutions have two parts
Solute – substance being dissolved
Solvent – substance doing the dissolving
With some solutions the solvent (water) can be evaporated and the solute (salt) dissolved reappears in crystal form.

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

15. Mineral Classification
Most mineral groups are based on the elements that are in the mineral.
Silicates – vast majority of the earth’s crust.
Ex: Quartz and Feldspar
Oxides – minerals that have oxygen in them.
Ex: Hematite and Magnetite
Sulfides – minerals that have sulfur in them.
Ex: Pyrite and galena
Halide – … have one of the halogens in them.
Ex: halite (NaCl) and Fluorite
Pure metal elements: Gold, silver, etc

16. Mineral Identification
Physical Properties of minerals allow for accurate identification
Hardness
Luster
Specific Gravity
Streak
Cleavage
Special Properties

17. Mineral Identification
HARDNESS SCALE
INDEX MINERAL
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
Hardness: determine by Mohs Scale

18. Mineral Identification
Luster: reflecting of light
The two main types of luster are metallic and nonmetallic.
Metallic luster
Nonmetallic Luster

19. Mineral Identification
Specific Gravity: Specific gravity is the "heaviness" of a mineral.
It is defined as a number that expresses the ratio between the weight of a mineral and the weight of an equal volume of water. Water has a specific gravity of 1.

20. Mineral Identification
Streak: is the color of the powder left on a streak plate

21. Mineral Identification
Cleavage: is the ability of a mineral to break along preferred planes.
Fracture: tendency of a mineral to break along curved surfaces without a definite shape

22. Mineral Identification
Special Properties of minerals
Transparency
Magnetism
Tenacity (how tough a mineral is)

23. Minerals Summary What makes something a mineral?
Five characteristics
Arrangement and organization of crystal structures
Unit Cell  lattices  Crystal systems
Formation of Minerals
From lava / Solutions
Mineral Identification
Based on physical properties

24. Assessment
Can I…
Identify and describe the criteria for crystals classification
Explain the concept of the Unit Cell and tell why it is necessary in explaining mineral structures
Determine the identity of minerals based ont their properties.