Steve Kadel, Glendale Community College

1. Atoms, Elements, and MineralsPhysical Geology 11/e, Chapter 2 Steve Kadel, Glendale Community College

2. Minerals A mineralis a ……. Consistent and recognizable physicaland chemical properties

3. Atoms and Elements An element … An atom … Composed of 3 types of subatomic particles 1 2 3 Amolecule …

4. Figure 2.4 The combining and conecting of atoms creates a compound

5. Atomic Structure Protons and neutrons form the nucleusof an atom Electrons orbit the nucleus in discrete shells or energy levels

6. Chemical Bonding Chemical bonding Elements will typically be reactive unless their valence shell is full. Ions… Positive and negative ions are attracted to one another by….

7. These two Clorine atoms have seven electrons in their outer shells, so they need one more. They can share their bonds to make them stronger. Thus covalent bonding. Sodium has an extra electron in outer shell so it gives up to Chlorine. Clorine needs one due to only having seven so it takes Na electron into outer shell. Ionic bonding http://ithacasciencezone.com/chemzone/lessons/03bonding/mleebonding/ionic_bonds.htm

8. Chemical Bonding • Ionic bonding • Covalent bonding • Metallic bonding Ionic bonding of NaCl (sodium chloride)

9. Helium has two electrons and fills the inner shell Everytime we add a proton, electron, or neutron, we change the atom, and if we change the atom, we change the element. The far right column has eight electron to fill outer shell thus they are “inert”.

10. Isotopes Atoms of an element with different numbers of neutrons are called isotopes Isotopes may be either stable or unstable Stable isotopes can be used to track climate change over time

11. Composition of Earth’s Crust • Common elements • Common mineral types • Minerals have crystalline structures • Regular 3-D arrangement of atoms

12. Notice the two most common elements: Oxygen and Silicon

13. Silicate Structures • The Silicon-Oxygen tetrahedron • Strongly bonded silicate ion • Basic structure for silicate minerals • Sharing of O atoms in tetrahedra • The more shared O atoms per tetrahedron, the more complex the silicate structure • Isolated tetrahedra (none shared) • Chain silicates (2 shared) • Double-chain silicates (alternating 2 and 3 shared) • Sheet silicates (3 shared) • Framework silicates (4 shared)

14. Non-silicate Minerals • Carbonates • Contain CO3 in their structures (e.g., calcite - CaCO3) • Sulfates • Contain SO4 in their structures (e.g., gypsum - CaSO4.2H2O) • Sulfides • Contain S (but no O) in their structures (e.g., pyrite - FeS2) • Oxides • Contain O, but not bonded to Si, C or S (e.g., hematite - Fe2O3) • Native elements • Composed entirely of one element (e.g., diamond - C; gold - Au)

15. Minerals • A mineral must meet the following criteria: • Crystalline solid • Atoms are arranged in a consistent and orderly geometric pattern • Rock-forming minerals • Although over 4000 minerals have been identified, only a few hundred are common enough to be generally important to geology (rock-forming minerals)

16. The structure of a mineral can be changed as in a diamond or graphite. Both are made of pure carbon, one is in sheets(graphite) and other is in a three dimensional structure(diamond). Chemically the same, but structurally they’re different minerals. http://www.avogadro.co.uk/structure/chemstruc/network/g-molecular.htm

17. Minerals • Ore minerals • Minerals of commercial value • Gemstones • Prized for their beauty • and (often) hardness

18. Mineral Properties • Physical and chemical properties of minerals are closely • linked to their atomic structures and compositions • Color • Streak • Luster • Hardness • Crystal form

19. Mineral Properties • Cleavage • Fracture • Specific gravity • Magnetism • Chemical reaction

20. The color of a mineral is one of its most obvious attributes, and is one of the properties that is always given in any description. Color results from a mineral’s chemical composition, impurities that may be present, and flaws or damage in the internal structure. Unfortunately, even though color is the easiest physical property to determine, it is not the most useful in helping to characterize a particular mineral.

21. The color of a mineral when it is powdered is called the streak of the mineral. Crushing and powdering a mineral eliminates some of the effects of impurities and structural problems, and is a better diagnostic for some minerals than their color. Streak can be determined for any mineral by crushing it with a hammer, but it is more commonly (and less destructively) obtained by rubbing the mineral across the surface of a hard, unglazed porcelain material called a streak plate. • The color of the powder left behind on the streak plate is the mineral's streak. The streak and color of some minerals are the same. For others, the streak may be quite different from the color, as for example the red-brown streak of hematite, often a gray to silver-gray mineral. Using luster, color, and streak may be enough to permit identification of the mineral.

22. The luster of a mineral is the way its surface reflects light. Most terms used to describe luster are self-explanatory: metallic, earthy, waxy, greasy, vitreous (glassy), adamantine (or brilliant, as in a faceted diamond). It will be necessary, at least at first, only to distinguish between minerals with a metallic luster and those with one of the non-metallic lusters. • A metallic luster is a shiny, opaque appearance similar to a bright chrome bumper on an automobile. • Other shiny, but somewhat translucent or transparent lusters (glassy, adamantine), along with dull, earthy, waxy, and resinous lusters, are grouped as non-metallic.

23. In some minerals, bonds between layers of atoms aligned in certain directions are weaker than bonds between different layers. Breakage will occur along smooth, flat surfaces parallel to zones of weakness. In some minerals, a single direction of weakness exists, but in others, two, three, four, or as many as six may be present. • It may be difficult for the beginner to distinguish between cleavage and crystal faces. After all, both are smooth, planar surfaces. Two hints will help make the distinction easy. • (1) If a mineral's outer surface shows tarnish, the crystal faces will be tarnished or dull; if cleavage planes are present, they may be recently made and will be fresher and less altered. • (2) If many surfaces are present parallel to one another, they are most likely cleavage surfaces.

24. The Mohs Hardness Scale is a relative scale. This means that a mineral will scratch any substance lower on the scale and will be scratched by any substance with a higher number. Diamond is not 10 times harder than talc or 1.1 times harder than corundum, as would be the case with an absolute hardness scale. Most often we are able only to narrow down hardness to within a certain range; for example, if an unknown mineral scratches a copper penny but does not scratch a glass plate, its hardness must be greater than 3.0 and less than 5.5. Usually this range of values is sufficient to identify an unknown.

25. When minerals form in environments where they can grow without interference from neighboring grains, they commonly develop into regular geometric shapes, or crystals, bounded by smooth crystal faces. The crystal form for a given mineral is governed by the mineral's internal structure, and may be distinctive enough to help identify the mineral. For example, quartz forms elongated, six-sided prisms capped with pyramid-like faces; galena and halite occur as cubes; and garnets develop 12- or 24-sided equidimensional forms. Interference from other mineral grains during growth may prevent formation of well-formed crystals. The result is shapeless masses or specimens that developed only a few smooth crystal faces. This type of specimen is much more common than well-formed crystals.

26. The specific gravity of a substance is a comparison of its density to that of water. To compare the specific gravity of any two minerals, simply hold a sample of one in your hand and "heft it," i.e., get a feeling for its weight. Then heft a sample of the other that is approximately the same size. If there is a great difference in specific gravity, you will detect it easily.

27. Magnetism - A few minerals are attracted to a magnet or are themselves capable of acting as magnets (the most common magnetic mineral is magnetite). • Feel - Some minerals, talc and graphite, feel greasy when you rub your fingers over them. The greasiness occurs because bonds are so weak in one direction that your finger pressure alone is enough to break them and to slide planes of atoms past neighboring atomic layers. • Taste - Taste is one of the last tests to be conducted, due to some minerals being poisonous. Some minerals taste salty-most notably halite (salt). Sylvite, which is similar to other halite properties, is bitter. NEVER TASTE A MINERAL UNLESS INSTRUCTED TO! • Reaction with Dilute Hydrochloric Acid - This is a chemical property rather than a physical attribute. Carbon dioxide is released from the mineral and bubbles out through the acid, creating the fizz. Some minerals such as Dolomite will react only in a powder form.

28. Igneous Rocks, Intrusive Activity, and the Origin of Igneous RocksPhysical Geology 11/e, Chapter 3 Steve Kadel, Glendale Community College

29. Rock An aggregate of one or more minerals

30. The Rock Cycle • A rock is a … • The rock cycle shows… • Representation of how rocks are formed, broken down, and processed in response to changing conditions • Processes may involve interactions of geosphere with hydrosphere, atmosphere and/or biosphere Rock that is weathered and not transported is called soil

31. The Rock Cycle and Plate Tectonics • Magma is created by melting of rock above a subduction zone • Less dense magma rises and cools to form igneous rock • Igneous rock exposed at surface gets weathered into sediment • Sediments transported to low areas, buried and hardened into sedimentary rock • Sedimentary rock heated and squeezed at depth to form metamorphic rock • Metamorphic rock may heat up and melt at depth to form magma

32. Igneous Rocks • Magma • Igneous rocks form when • Intrusive igneous rocks form when magma • Extrusive igneous rocks form http://www.pitt.edu/~cejones/GeoImages/2IgneousRocks.html Granite Basalt Notice the grain size of intrusive and extrusive

33. Igneous Rock Textures • Texture refers to the size, shape and arrangement of grains or other constituents within a rock • Texture of igneous rocks is primarily controlled by cooling rate • Extrusive igneous rockscool quickly at or near Earth’s surface and are typically fine-grained (most crystals <1 mm) • Intrusive igneous rockscool slowly deep beneath Earth’s surface and are typically coarse-grained (most crystals >1 mm) Fine-grained igneous rock Coarse-grained igneous rock

35. Igneous Rock Identification • Igneous rock names are based on texture (grain size) and mineralogiccomposition

36. Table 3.2

37. Special Igneous Textures • A pegmatite • A glassy texture • A porphyritic texture Pegmatitic igneous rock Porphyritic igneous rock

38. Igneous Rock Identification • Igneous rock names are based on texture (grain size) and mineralogic composition • Textural classification • Plutonic rocks (gabbro-diorite-granite) • Volcanic rocks (basalt-andesite-rhyolite) • Compositional classification • Mafic rocks (gabbro-basalt) • Intermediate rocks (diorite-andesite) • Felsic rocks (granite-rhyolite)

39. Igneous Rock Chemistry • Rock chemistry, particularly silica (SiO2) content, determines mineral content and general color of igneous rocks • Mafic rocks • Felsic (silicic) rocks • Intermediate rocks • Ultramafic rocks have

40. Intrusive Rock Bodies • Intrusive rocks exist in bodies or structures that penetrate or cut through pre-existing country rock • Intrusive bodies are given names based on their size, shape and relationship to country rock • Shallow intrusions: Dikes and sills • Form <2 km beneath Earth’s surface • Chill and solidify fairly quickly in cool country rock • Generally composed of fine-grained rocks Insert new Fig. 3.11 here

41. Intrusive Rock Bodies • Intrusive rocks exist in bodies or structures that penetrate or cut through pre-existing country rock • Intrusive bodies are given names based on their size, shape and relationship to country rock • Deep intrusions:

42. Intrusive Rock Bodies • Volcanic neck • Dike • Sill • Pluton • Large, • Small plutons

43. How Magma Forms • Heat from below • Heat vs. pressure

44. How Magma Forms • Hot water under pressure • Mineral mixtures

45. Magma Crystallization and Melting Sequence • Minerals crystallize in a predictable order (and melt in the reverse order), over a large temperature range, as described by Bowen’s Reaction Series • Discontinuous branch • Continuous branch Bowen’s Reaction Series

46. Lessons from Bowen’s Reaction Series • Large variety of igneous rocks is produced by large variety of magma compositions • Mafic magmas will crystallize into basalt or gabbro if early-formed minerals are not removed from the magma • Intermediate magmas will similarly crystallize into diorite or andesite if minerals are not removed • Separation of early-formed ferromagnesian minerals from a magma body increases the silica content of the remaining magma • Minerals melt in the reverse order of that in which they crystallize from a magma

47. Magma Evolution • A change in the composition of a magma body is known as magma evolution, due to Bowen’s reaction series. • Magma evolution can occur by differentiation, partial melting, assimilation, or magma mixing • Differentiation • Partial melting

48. Magma Evolution • Assimilation • Magma mixing Insert new Fig. 3.22 here Insert new Fig. 3.23 here

49. Igneous Activity and Plate Tectonics • Igneous activity occurs primarily at or near tectonic plate boundaries • Mafic igneous rocks are commonly formed at divergent boundaries • Intermediate igneous rocks are commonly formed at convergent boundaries

50. Igneous Activity and Plate Tectonics • Felsic igneous rocks are commonly formed adjacent to convergent boundaries • Intraplate volcanism