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Matter and Minerals

Matter and Minerals. Elements and the Periodic Table. Matter.  Elements are the b asic building blocks of minerals. .  Over 100 elements are known. Atoms. Matter.  Smallest particles of matter.  Have all the characteristics of an element.

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Matter and Minerals

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  1. Matter and Minerals

  2. Elements and the Periodic Table Matter  Elements are the basic building blocks of minerals.  Over 100 elements are known.

  3. Atoms Matter Smallest particles of matter Have all the characteristics of an element The nucleusis the central part of an atom and contains • protons, which have positive electrical charges • neutrons, which have neutral electrical charges

  4. Atoms Matter Energy levels, or shells • surround the nucleus • contain electrons—negatively charged particles  The atomic number is the number of protons in the nucleus of an atom.

  5. Model of an Atom

  6. Isotopes Matter Isotopes of an element have the same number of protons but varying numbers of neutrons. Have different mass numbers: the sum of the neutrons plus protons Many isotopes are radioactive and emit energy and particles. The mass number is the number of neutrons and protons in the nucleus of an atom.

  7. Why Atoms Bond Matter When an atom’s outermost energy level does not contain the maximum number of electrons, the atom is likely to form a chemical bond with one or more atoms. • A compound consists of two or more elements that are chemically combined in specific proportions. • An ion is an atom that gains or losses electrons.

  8. Types of Chemical Bonds Matter 1. Ionic bonds form between positive and negative ions. 2. Covalent bonds form when atoms share electrons. 3. Metallic bonds form when metal ions share electrons.

  9. Minerals: the building blocks of rocks • Definition of a Mineral: • naturally occurring • inorganic • solid • characteristic crystalline structure • definite chemical composition

  10. How do we identify minerals? • Physical properties: • Color • Luster • Hardness • Crystal shape • Cleavage • Specific gravity • Other

  11. Physical Properties of Minerals • Color: • Most obvious, but often misleading • Different colors may result from impurities Example: Quartz

  12. Physical Properties of Minerals • Color: Streak – color of a mineral in powdered form (used for metallic minerals) Obtained by scratching a mineral on a piece of unglazed porcelain. Example: Hematite

  13. Streak • Red chalk on a chalk board makes red marks. White chalk makes white marks. • Not all minerals work this way. When some minerals are scratched along a ceramic streak plate, it creates a different color.

  14. Gold • When gold is run across a streak plate it makes a yellowish-gold color. • That makes sense.

  15. Pyrite or “Fool’s Gold” • When pyrite is run across a streak plate, it has a black or dark green streak. • Pyrite is not worth much money, while gold is worth a lot. They look alike, so miners call it fool’s gold.

  16. Hematite • Hematite’s color is grey, but its streak is red. • Hema means blood. • The mineral was named hematite because it looked like it was bleeding when it was taken across a streak plate.

  17. One mineral property we will not use… COLOR

  18. A mineral can be many different colors. Below is Mica.

  19. Many minerals can be the same color. Below are gold colored minerals. Which one is gold?

  20. The answer… None of them were real gold.

  21. Just like with people… Outside color does not tell you much about the important characteristics.

  22. Physical Properties of Minerals • Luster: • How a mineral surface reflects light • Two major types: • Metallic luster • Non-metallic luster Metallic example: Galena Non-metallic example: Orthoclase

  23. Pyrite (Fool’s Gold) Displays Metallic Luster.

  24. Physical Properties of Minerals • Hardness: • How easy it is to scratch a mineral • Mohs Scale of Hardness • relative scale • consists of 10 minerals, ranked 1 (softest) to 10 (hardest)

  25. Hardest (10) – Diamond Softest (1) – Talc Common objects: - Fingernail (2.5) - Copper penny (3.5) - Wire nail (4.5) - Glass (5.5) - Streak plate (6.5) Mohs Scale of Hardness

  26. Hardness • Is measured by how easy it is to scratch. • Geologists order the hardness by… • Scratched by a fingernail. • Scratched by a penny. • Scratched by a nail. • Scratched by a diamond. These are not all of the tools geologists use, but it will work for our experiment.

  27. Gypsum is soft, it can be scratched by a fingernail.

  28. Calcite is soft, but a little harder because it cannot be scratched by a fingernail, but it can be scratched by a penny.

  29. Fluorite is harder. It can be scratched by a nail, but not a penny or fingernail.

  30. Diamonds are the hardest mineral, so it scratches every mineral.

  31. Physical Properties of Minerals • Crystal shape (or form): • external expression of a mineral’s internal atomic structure • planar surfaces are called crystal faces • angles between crystal faces are constant for any particular mineral Pyrite Quartz

  32. Physical Properties of Minerals • Cleavage vs. Fracture: • The way a mineral breaks • Cleavage: tendency of a mineral to break along planes of weakness • Minerals that do not exhibit cleavage are said to fracture • Do not confuse cleavage planes with crystal faces! Crystal faces are just on the surface and may not repeat when the mineral is broken.

  33. Physical Properties of Minerals • Cleavage is described by: • Number of planes • Angles between adjacent planes • These are constant for a particular mineral

  34. Physical Properties of Minerals • Cleavage (1 direction): Example: mica

  35. Mica Has Cleavage in One Direction

  36. Physical Properties of Minerals • Cleavage (2 directions): orthoclase amphibole

  37. Physical Properties of Minerals • Cleavage (3 directions): halite calcite

  38. Physical Properties of Minerals • Cleavage (4 directions): fluorite

  39. Physical Properties of Minerals • Fracture: • minerals that do not exhibit cleavage are said to fracture • smooth, curved surfaces when minerals break in a glass-like manner: conchoidal fracture Quartz

  40. Conchoidal Fracture

  41. Physical Properties of Minerals • Specific gravity: • weight of a mineral divided by weight of an equal volume of water • metallic minerals tend to have higher specific gravity than non-metallic minerals Galena SG=7.5 Quartz SG=2.67

  42. Physical Properties of Minerals • Other properties: • reaction with hydrochloric acid(calcite fizzes) • taste(halite tastes salty) • feel(talc feels soapy, graphite feels greasy) • magnetism(magnetite attracts a magnet)

  43. Mineral Groups • Rock-forming minerals • ~30 common minerals make up most rocks in Earth’s crust • Composed mainly of the 8 elements that make up over 98% of the crust

  44. Mineral Groups Element Abundances Silica (SiO4)4- SILICATES Common cations that bond with silica anions All others: 1.5%

  45. Mineral Groups • Silicates (most abundant) • Non-silicates (~8% of Earth’s crust) • Oxides O2- • Carbonates (CO3)2- • Sulfides S2- • Sulfates (SO4)2- • Halides Cl-, F-, Br- • Native elements (single elements; e.g., Au)

  46. Mineral Groups Non-ferromagnesian Silicates (K, Na, Ca, Al) Ferromagnesian Silicates (Fe, Mg) Oxides Carbonates Sulfides/sulfates Native elements

  47. Mineral Groups – Silicates Silicon-oxygen tetrahedron (SiO4)4- 1. Silicates • Tetrahedron • fundamental building block • 4 oxygen ions surrounding a much smaller silicon ion

  48. Mineral Groups – Silicates • Joining Silicate Structures • How tetrahedra may be linked: • independent tetrahedra • single chains • double chains • sheets • 3-D framework

  49. Mineral Groups– Silicates –

  50. Mineral Groups – Silicates Olivine Group dark silicates (Fe-Mg)  ferromagnesian No cleavage

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