1. Chapter 1 Minerals: Building Blocks of Rocks

2. Minerals: Building Blocks of Rocks
By definition a mineral is/has
Naturally occurring
Solid
Ordered internal molecular structure
Definite chemical composition
Generally inorganic
Rock
A solid aggregate of mineral, or mineral like, matter that occurs naturally

3. 01_03

4. Composition and Structure of Minerals
Elements
Basic building blocks of minerals
Over 100 are known (92 naturally occurring)
most minerals are compounds (formed when 2 or more elements chemically combine)
Atoms
Smallest particles of matter
Retain all the characteristics of an element
the atoms of elements combine to form
compounds

5. Composition and Structure of Minerals
Atomic structure
Central region called the nucleus
Consists of protons (+ charges) and neutrons (no charges)
atomic number=number on protons, this
determines identity of the element
Electrons
Negatively charged particles that surround the nucleus
Located in discrete energy levels (shells)
determine chemical properties of element

6. Structure of an Atom
Figure 1.5 A

7. 01_05B

8. Composition and Structure of Minerals
Chemical bonding
Formation of a compound by combining two or more elements
Atoms gain (-) or lose (+) outermost electrons to form ions, to satisfy
octet rule.
Oppositely charged ions attract one another to produce a neutral chemical compound by forming ionic bonds

9. 01_06

10. Composition and Structure of Minerals
Isotopes and radioactive decay
Mass number = sum of neutrons + protons in an atom
Isotope = atom that exhibits variation in its mass number
atomic weight(mass)=weighted av. of mass numbers for isotopes of an element
Unstable nuclei of some isotopes emit particles and energy in a process known as radioactive decay
The precise rate of decay is useful
for dating purposes (radiometric dating)

11. Physical Properties of Minerals
Crystal form
External expression of a mineral’s internal structure
Often interrupted due to competition for space and rapid loss of heat

12. Quartz

13. A Garnet Crystal

14. Cubic Crystals of Pyrite
Figure 1.7 A

15. Physical Properties of Minerals
Luster
Appearance of a mineral in reflected light
Basic categories
Metallic-appearance of a metal
Nonmetallic
includes descriptive terms include vitreous, silky, or earthy
submetallic-appear slightly metallic

16. Galena (PbS) Displays Metallic Luster
Figure 1.13

17. Physical Properties of Minerals
Color
Generally unreliable for mineral identification
Often highly variable due to slight changes in mineral chemistry
Exotic colorations (due to impurities)of certain minerals produce gemstones
Inherent coloration is the true color of the mineral

18. Quartz (SiO2) Exhibits a Variety of Colors

19. Physical Properties of Minerals
Streak
Color of a mineral in its powdered form
dark streak-metallic
light streak- nonmetallic
Hardness
Resistance of a mineral to abrasion or scratching
All minerals are compared to a standard scale called the Mohs scale of hardness

20. Streak Is Obtained on an Unglazed Porcelain Plate
Figure 1.8

21. Mohs Scale of
Hardness
Figure 1.9

22. Physical Properties of Minerals
Cleavage
Tendency to break along planes of weak bonding
Produces flat, shiny surfaces
Described by resulting geometric shapes
Number of planes
Angles between adjacent planes

23. 01_17C

24. Fluorite, Halite, and Calcite All Exhibit Perfect Cleavage
Figure 1.11

25. Physical Properties of Minerals
Fracture
Absence of cleavage when a mineral is broken
Specific Gravity
Weight of a mineral/weight of an equal volume of water
Average value = 2.5 – 3.0

26. Conchoidal Fracture
Figure 1.12

27. Physical Properties of Minerals
Other properties
Magnetism
Reaction to hydrochloric acid
Malleability
Double refraction
Taste
Smell
Elasticity

28. Mineral Groups Nearly 4000 minerals have been named
Rock-forming minerals
Common minerals that make up most of the rocks of Earth’s crust
Only a few dozen members
Composed mainly of the 8 elements that make up over 98% of the continental crust

29. Elemental Abundances in Continental Crust
Figure 1.14

30. Mineral Groups Silicates-(dark and light) Most important mineral group
Comprise most rock-forming minerals
Very abundant due to large % of silicon and oxygen in Earth’s crust
most crystallize from molten rock as it cools
Silicon-oxygen tetrahedron
Fundamental building block
Four oxygen ions surrounding a much smaller silicon ion

31. Two Illustrations of the Si–O Tetrahedron
Figure 1.15

32. 01_16

33. Mineral Groups Common silicate minerals Feldspar group Quartz
Most common mineral group
Quartz
Only common silicate composed entirely of oxygen and silicon

34. Potassium Feldspar
Figure 1.17

35. Quartz

36. Mineral Groups Important nonsilicate minerals
Comprise only 8% of Earth’s crust
Often occur as constituents in sedimentary rocks

37. Table 1.1

38. Mineral Groups Important nonsilicate minerals Carbonates
Primary constituents in limestone and marble
Limestone is used commercially for road paving, building stone, and as the main ingredient in Portland cement

39. Mineral Groups Important nonsilicate minerals
A number of other minerals have economic value
Examples
Hematite (oxide mined for iron ore)
Sphalerite (sulfide mined for zinc ore)
Galena (lead)
Native copper (native element mined for copper)

40. Mineral Groups Important nonsilicate minerals Halite and gypsum
Both are commonly found in thick layers
Like limestone, both halite and gypsum are important nonmetallic resources

41. Native Copper

42. End of Chapter 1