1. Rocks and Minerals A First Look
Chapter 2
Rocks and Minerals A First Look
The differences in the physical properties of rocks, minerals, and soils determine their suitability for different purposes – extraction of water or of metals, construction, manufacturing, waste disposal, agriculture, and other uses

2. Atoms
Smallest particle into which an element can be divided while still retaining the chemical characteristics of that element
Composed of a nucleus surrounded by electrons
Nucleus is composed of protons (+) and neutrons (0)
Number of protons defines the chemical element and atomic number ( H = 1, He = 2, Li = 3, …)
Number of neutron adds mass to the atom
Number of electrons (-) orbiting nucleus determined by the number of positively charged protons;
Negatively charged electrons balance the positive charges of the protons

3. Figure 2.1 Schematic drawing of atomic structure

4. Elements and Isotopes
Element – substance composed of atoms with the same number of protons
All nuclei, except the simplest hydrogen atoms, contain neutrons
The number of neutrons is similar to or somewhat greater than the number of protons
Isotopes – number of neutrons for and element may not be the same; variable numbers of neutrons possible
Atomic Mass Number is the number of protons and neutrons in the elements nucleus
Some isotopes have more neutron and are heavier (carbon-14 has 6 protons and 8 neutrons)
Some isotopes have fewer neutrons and are lighter (carbon-12 has 6 protons and 6 neutrons)

5. Ion An atom that is positively charged or negatively charged
Anion have gained electrons (-); has more electrons relative to the number of protons (+)
Cation has lost electrons (-); has fewer electrons relative to the number of protons (+)
The electrical attraction of ions will cause an ionic bond to form between oppositely charged ions.
Na+ + Cl- = NaCl (halite)

6. Compounds
Mixing of two or more chemical elements in particular proportions that have distinctive physical properties
Elements will bond because of electrical attraction, forming ionic bonds, or the atoms may share electrons, forming covalent bonds

7. MINERALS Naturally occurring Inorganic Solid element or compound
Definite chemical composition
Regular internal crystal structure
Identified by recognizing different physical properties

8. Figure 2.3A

9. Figure 2.3B

10. Identifying Minerals
The two fundamental characteristics of a mineral are its chemical composition and its crystal structure
Analyze the mineral composition
Technology based
Measure crystal structure and symmetry
Observe and measure physical and special properties
Easy for humans to see and recognize

11. Mineral Physical Properties
Color
Hardness
Cleavage
Luster
Density
Crystalline Form

13. Mineral Composition Silicate Group
Silicate group – variety of compounds based on silicon and oxygen
Quarts – glass manufacturing
Feldspar – ceramic manufacturing
Mica
Muscovite (white mica)
Biotite (dark mica)
Clays – used as drilling mud, in building materials, and as a soil modifier
Ferromagnesian silicates
Olivine – peridot (semiprecious gem)
Garnet - abrasives
Asbestos – industrial products

14. Figure 2.6

15. Figures 2.7 a and b

16. Mineral Composition Nonsilicates
Carbonates – CO3
Useful for building materials and manufacturing
Sulfates – SO4
Useful for building materials
Sulfides – S
Host for many metallic ores (Pb, Cu, Zn, and others)
Oxides – any metal combined with oxygen
Iron and aluminum ores
Native elements – minerals composed of single element
Carbon as diamond and graphite
Cooper, gold, silver, or platinum

17. Figures 2.2 c and d

18. Figures 2.3 a and b

19. Figure 2.4

20. Figures 2.5 a and b

21. Rocks – formed from Minerals
A solid aggregate of one or more minerals, or mineral materials
Consists of many mineral grains or crystals forming a solid mass
Each rock contains a record of its own history
Three broad categories
Igneous
Sedimentary
Metamorphic

22. Igneous Rocks
Magma, at high enough temperatures, rocks and minerals can melt, and the natural hot, molten rock material is called magma
Silicates are the most common minerals, and magmas are thus rich in silica. Magmas also contain some dissolved water and gases, and include some solid crystals suspended in the melt
An igneous rock is a rock formed by the solidification and crystallization of a cooling magma

23. Igneous Rocks
Rocks formed from hot, molten rock material – “fire” rocks
Usually composed of silicate minerals and some dissolved gases and water
Molten materials are very hot
Plutonic rocks form if magma does not flow onto surface; coarse crystals will grow
Volcanic rocks form if magma flows onto surface as lava; glass often forms

24. Figures 2.10 a and b

25. Igneous Rocks
Granite is the most widely known example of a plutonic rock, consisting of quartz, feldspars, and some ferromagnesian minerals or other silicates
Granites show the characteristic of a plutonic rock: the coarse and interlocking crystals
Lava, a magma that flows out on the earth’s surface while still wholly or partly molten
Volcanic, an igneous rock formed at or close to the earth’s surface
Basalt, the most common volcanic rock, rich in ferromagnesian minerals and feldspar

26. Weathering of Rocks Chemical weathering Physical weathering Sediments
Ions for cements

27. Sedimentary Rocks
Sediments are produced by weathering of pre-existing rocks and minerals
Sediments are loose, unconsolidated accumulations of mineral or rock particles
Sediments are eroded, transported, and deposited in many sedimentary environments
The sediments will be buried and experience lithification
Lithification involves compacting the sediments with burial and cementation of the sediments forming a sedimentary rock

28. Sedimentary Rocks
Gravity plays a role in the formation of all sedimentary rocks.
Layering is a very common feature of sedimentary rocks and is used to identify the origins of sedimentary rocks.
Sedimentary rocks can yield information about the settings in which the sediments were deposited.
Sedimentary rocks are formed at or near the earth’s surface and at temperatures close to ordinary surface temperatures.

29. Types of Sedimentary Rocks
Clastic sedimentary rocks
Formed by the lithification of mechanically broken up pieces of rocks and minerals
Grain sizes range from boulder, gravel, sand, silt, and mud
Grains are continually broken down in size and shape until deposited
Once deposited these clastic particles a cemented
Chemical sedimentary rocks
Chemical process occur in water bodies such as lakes, seas, or oceans
Minerals precipitate from the water form thick deposits
Examples: Halite, Calcite, and Gypsum

30. Figures 2.11 Sedimentary Rocks

31. Figures 2.11 Sedimentary Rocks

32. Metamorphic Rocks “Changed form” rock
Rock formed from pre-existing rock or minerals
Heat, pressure, and chemical active fluids cause changes in rock
Heat increases as a rock is buried or is close to a magma chamber
Pressure increases with burial or collision between moving continents
Fluids become heated and circulate with burial or with location near a magma chamber

33. Metamorphic Rocks
The temperatures required to form metamorphic rocks are below magmatic temperatures
Significant changes can occur in a rock at temperatures well below melting
Temperature and pressure can cause the minerals in the rock to recrystallize
Pressure may cause the rock to be deformed
The sources of elevated temperatures of metamorphism: burial, magma, mountain-building, and plate tectonic movement
The sources of elevated pressures of metamorphism: burial, mountain-building, and plate tectonic movement

34. Types of Metamorphism
Contact metamorphism – localized metamorphism of rocks adjacent to a magma chamber
Regional metamorphism – large scale stressing and heating of a rock by deep burial or continental plates moving and colliding

35. Common Metamorphic Rocks
Any kind of preexisting rock (another rock) can be metamorphosed
Foliation: when a rock is subjected to directed stress, its minerals form elongated/platy crystals and line up parallel to each other
Metamorphic rocks without foliation do not directed stress
Marble is metamorphosed limestone
Quartzite is metamorphosed quartz-rich sandstone
Metamorphic rocks with foliation show directed stress or pressure
Slate – low grade foliated metamorphic rock
Schist and Gneiss (nice) – high grade metamorphic rocks

36. Figures 2.12 Metamorphic rocks have undergone mineralogical, chemical, and/or structural change

37. Figures 2.12 Metamorphic rocks have undergone mineralogical, chemical, and/or structural change

38. The Rock Cycle
Three rock groups on the basis of their mode of origin: igneous, sedimentary, and metamorphic
Shows the interrelationships among the three rock types
Rocks of any type can be transformed into rocks of another type or into another distinct rock of the same general type through the geologic processes
Rocks are continually being changed by geological processes

39. The Rock Cycle Earth as a system: the rock cycle
Magma, a molten material formed inside Earth
Crystallization, magma cools and solidifies
Igneous rock, formed by “fire” underneath
Weathering, transportation, and deposition
Sediment
Lithification
Sedimentary rock
Metamorphism
Metamorphic rock
Melting
Magma

40. The Rock Cycle Earth as a system: the rock cycle
Full cycle does not always take place due to "shortcuts" or interruptions
e.g., Sedimentary rock melts
e.g., Igneous rock is metamorphosed
e.g., Sedimentary rock is weathered
e.g., Metamorphic rock weathers
Through time, geologic processes acting on older rocks change them into new and different ones so that, in a sense, all kinds of rocks are interrelated

41. Fig The Rock Cycle

42. The Rock Cycle The Essence of the Rock Cycle
Igneous rocks, formed from magma
Sedimentary rocks, formed from low-temperature accumulations of particles or by precipitation from solution
Metamorphic rocks, formed from preexisting rocks through the change of temperature and pressure
Geologic processes working on old rocks change the old rocks into new and different ones, and thus all kinds of rocks are interrelated in a sense