1. Minerals Chapter 2 Instructor : Pete Kozich
Earth Science 101
Minerals Chapter 2
Instructor : Pete Kozich

2. Minerals: the building blocks of rocks
Definition of a mineral
Natural
Inorganic
Solid
Possess an orderly internal structure of atoms
Have a definite chemical composition
Rock – any solid mass of mineral, or mineral-like material that occurs naturally

3. What is a Rock? An aggregate (mixture) of minerals
Each mineral within the rock retains its own identity
Note a large quantity of one mineral may also be considered a Rock
Calcite—the rock, limestone

4. Composition and structure of minerals
Elements
Basic building blocks of minerals
Over 100 are known
Some minerals are made of entirely one element (e.g., Gold, Sulfur)
Most individual elements are unstable
Most minerals are a combination of two or more unstable elements that form a stable compound
Atoms
Tiny particles of matter
Retains all the characteristics of an element
There are more atoms in an 8 oz glass of water than there are grains of sand on all the beaches in the world and more atoms in a mole than stars in the universe!!

5. Periodic table of the Elements
Figure 2.4

6. Varying mass number of Elements
Isotopes
A variation of an element
Have varying number of neutrons but the same number of protons
Have different mass numbers – the sum of the neutrons plus protons
Many isotopes are radioactive
emit energy and particles
Unstable

7. How atoms are constructed
Empty space occupies the greatest volume of any atom.
Nucleus – central part of an atom that contains
Protons – positive electrical charges
Neutrons – neutral electrical charges
Energy levels, or shells
Surround nucleus
Contain electrons – negative electrical charges

8. Simplified view of the atom
Figure 2.5

9. How atoms are constructed
Atomic number is the number of protons in an atom's nucleus
Determines the name and nature of the element
6 Protons = Carbon, 8 Protons = Oxygen
Neutral atoms have the same number of protons and electrons (charges balance)
Bonding of atoms
Forms a compound with two or more elements
H20, CH4, NaCl
Most are not easily separable
Elements do not maintain individual characteristics
Ionic Bond – transfer of electrons
Ions are atoms that gain or lose electrons
If they lose an electron – they have a positive charge
If they gain an electron – they have a negative charge
Covalent Bond – atoms share electrons

10. Chemical Bonds
Bonds. Chemical bonds join atoms. We will look at 2 out of the four types of chemical bonds.
Atoms of any element want their electron shells full or stable.
Ionic Bonds
Each element has a different number of protons. A stable electron shell may result in a different number of protons than electrons.
Ionic bonds result from negative and positive ions bonding together from attraction and fill their electron shells.
Covalent Bonds
Atoms that are not electrically charged which share electrons to fill their electron shells.

11. Minerals Physical properties of minerals Crystal form Luster Color
External expression of a mineral’s internal orderly arrangement of atoms
Needs sufficient space and time to form
Luster
Appearance or quality of light reflected from a surface of a mineral
Metallic, non-metallic, vitreous (glassy), pearly, silky, resinous, earthy (dull)
Color
Use cautiously as slight impurities in the mineral can change its color
Streak
Color of a mineral in its powdered form
Found using a “streak plate”
As a whole, much more useful than apparent color of the mineral

12. The mineral quartz often exhibits good crystal form

13. Pyrite (fool’s gold) displays metallic luster
Figure 2.10

14. Minerals Physical properties of minerals (continued) Hardness Cleavage
Resistance of a mineral to scratching
One of the most useful properties
Cleavage
The tendency of a mineral to cleave/break along planes of weak bonding
Results in pieces that have similar geometry
Tends to form straight/smooth surfaces
Described by the number of planes exhibited and the angles at which they meet
Fluorite (four planes)
Halite (three planes at 90 degrees)
Calcite (three planes at 75 degrees)

15. Mohs scale
of hardness

16. Three examples of perfect cleavage – fluorite, halite, and calcite

17. Minerals Physical properties of minerals Fracture Specific gravity
Minerals that do not exhibit cleavage when broken are said to fracture (opal, for example)
Fracture irregularly (Conchoidal Fracture – breaking in a glasslike manner)
Specific gravity
Compares a mineral’s weight with that of an equal amount of water
Example: If a volume of a mineral weighs three times more than the same amount of water, then that mineral has a specific gravity of 3.0
Other useful mineral properties
Taste
Smell
Elasticity
Malleability
Feel
Magnetism
Double Refraction
Reaction to hydrochloric acid

18. Conchoidal fracture
Figure 2.15

19. Minerals A few dozen minerals are called the rock-forming minerals
The eight elements that compose most rock-forming minerals are
oxygen (O) silicon (Si)
aluminum (Al) iron (Fe)
calcium (Ca) sodium (Na)
potassium (K) magnesium (Mg)
Most abundant atoms in Earth's crust are oxygen (46.6% by weight) and silicon (27.7% by weight)
O and Si are nonmentals, Fe a transition metal, rest are metals

20. Composition of continental crust
Figure 2.16

21. Minerals Mineral groups Rock-forming silicates
Most common mineral group
Contain the silicon-oxygen tetrahedron (molecule)
Four oxygen atoms surrounding a much smaller silicon atom
Combines with other atoms to form the various silicate structures
Formation
Crystallize from molten materials as it cools
Form from weathering of other silicates (clay)
Form from extreme pressure

22. The silicate (SiO4)-4 molecule
Figure 2.17

23. Minerals Mineral groups Rock-forming silicates
Groups based upon tetrahedral arrangement
Olivine – independent tetrahedra
Pyroxene group – tetrahedra are arranged in chains
Amphibole group – tetrahedra are arranged in double chains
Micas – tetrahedra are arranged in sheets
Two types of mica are biotite (dark) and muscovite (light)
Feldspars - Three-dimensional network of tetrahedra
Most plentiful mineral group
Two types of feldspar are Orthoclase and Plagioclase
Quartz – three-dimensional network of tetrahedra

24. Hornblende – a member of the amphibole group

25. Potassium feldspar

26. Plagioclase feldspar

27. Minerals Mineral groups Nonsilicate minerals Major groups
Oxides
Sulfides/Sulfates
“Native” elements
Gold, Diamonds, Graphite
Carbonates
A major rock-forming group
Found in the rocks limestone and marble
Halite (table salt) and gypsum (plaster) are found in sedimentary rocks
Many have economic value

28. Native Copper

29. Minerals Mineral resources Reserves Ores
Already identified deposits
Ores
Useful metallic minerals that can be mined at a profit
Economic factors may change and influence a resource

30. An underground halite (salt) mine