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What is a Mineral?

What is a Mineral?. What Exactly is a Mineral?. Compositionally and physically distinct substance Four criteria to be a true mineral…. Naturally Occurring. Created through natural geologic processes. Synthetic diamond: not a mineral. Raw diamond: mineral. Inorganic.

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What is a Mineral?

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  1. What is a Mineral?

  2. What Exactly is a Mineral? • Compositionally and physically distinct substance • Four criteria to be a true mineral…

  3. Naturally Occurring Created through natural geologic processes Synthetic diamond: not a mineral Raw diamond: mineral

  4. Inorganic That is, they do not consist of carbon-hydrogen molecules that may also form crystalline substances through biological processes Sugar: It looks like a mineral, but is it? Nope. Note the C-H bonds.

  5. Solid Liquid water Snowflake—frozen water Not a mineral Mineral…believe it or not

  6. Definite Chemical Composition Minerals are complex assemblages of multiple elements Chemical Formula Types of atoms involved and relative proportions Ex. Quartz Ex #2: Elbaite Chemical formula SiO2 Chemical formula Na(Li,Al)3Al6(BO3)3Si6O18(OH)4

  7. Elements • Pure chemical substance composed of one type of atom (i.e. specific # of protons…) • 88 naturally occurring elements • Most common (i.e. compose 98% of the earth’s crust—and therefore, minerals) • Oxygen, silicon, aluminum, iron, calcium, magnesium, potassium, and sodium

  8. Atomic Structure • Atom • Basic unit of an element • Very, very, very small (1/10,000,000,000 m) • Nucleus • Protons (+) • Neutrons (neutral) • Electrons (-) • “cloud” surrounding nucleus—exist in “shells” • Mostly empty space

  9. Visualizing the size of an atom • The nucleus is very small compared to the overall size of an atom • Imagine 5 ½ football fields (minus end zones) placed end to end (100 yrds long x 160’ wide) • Nucleus is like a grain of sand in the middle of them

  10. It’s All About the Electrons, Baby… • A stable atom is one in which the outermost shell of electrons is completely filled • Atoms can fill their outer shells by bonding to other atoms • Ionic bonding • Covalent bonding

  11. Bonding in a [Nut] Shell… • Ionic Bonding • Cations (atoms that have lost an electron) are attracted to anions (atoms that have gained an extra electron) • Neutral compounds • Weaker but more common than covalent bonds

  12. Bonding in a [Nut] Shell… • Covalent bonding • Two or more atoms share their electrons, producing the effect of filled outer electron shells • Very strong bond

  13. Crystalline Structure Halite • Arrangement of atoms are • Orderly • Regular • 3-D • Repeating pattern Biotite Fluorite

  14. Can You Spot the Mineral Wannabes? Pyrite FeS2 Silicon Carbide SiC oil Chalcanthite CuSO4-5H2O

  15. Growing a Mineral • Unit cell—smallest unit structure of a mineral • Brick Wall example

  16. Growing a Mineral: Halite Halite unit cell Halite crystal What halite looks like to us

  17. Identifying a Mineral • All minerals have physical and chemical properties that can be easily recognized • Direct result of structure and composition • Crystal habit • Cleavage • Fracture • Hardness • Color • Streak • Luster

  18. Cleavage • Not the kind you’re thinking of… • The tendency of a mineral to break along flat surfaces • Governed by bond strength and crystal structure • Stronger bonds = poor or no cleavage→

  19. Oooo…shiny! • Luster • The way a mineral reflects light • A metallic mineral is said to have a metallic luster • Those that do not have a metallic luster (non-metallic) are assigned names that are self-explanatory • Pearly, resinous, earthy, glassy, etc… Pyrite has a metallic luster Quartz has a glassy luster

  20. School of Hard Knocks… • Hardness • Resistance of a mineral to scratching • Hardness can be determined by scratching mineral with an object of known hardness • Scale—Mohs • Based on 10 minerals: 1 being talc and 10 being diamond

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