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MINERALS

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  1. MINERALS • Introduction • What Are They? • Atoms & Elements • Physical Properties & Identification • Mineral Groups

  2. Minerals Introduction

  3. GEOL 131: Minerals - Intro Eight Most Abundant Elements in Earth’s Crust

  4. GEOL 131: Minerals - Intro

  5. GEOL 131: Minerals - Intro Some of the Most Abundant Minerals in Earth’s Crust • Quartz • Feldspars • Micas

  6. GEOL 131: Minerals - Intro Some of the Most Abundant Minerals in Earth’s Crust • Amphiboles • Pyroxenes • Olivine e

  7. Minerals Minerals What Are They?

  8. GEOL 131: Minerals – What Are They? Minerals Are: • Solid • Naturally occurring • Inorganic

  9. GEOL 131: Minerals – What Are They? Minerals Have: • Well-defined chemical compositions • Well-ordered atomic structures

  10. Minerals Atoms & Elements

  11. All Minerals Are Made of Atoms GEOL 131: Minerals – Atoms and Elements

  12. GEOL 131: Minerals – Atoms and Elements The Periodic Table of the Elements http://www.ptable.com/

  13. Basic Structure of an Atom GEOL 131: Minerals – Atoms and Elements

  14. Valence Shells GEOL 131: Minerals – Atoms and Elements

  15. Atomic Bonds GEOL 131: Minerals – Atoms and Elements • Hold atoms together to make mineral crystals • Formed by electron interaction • Require filled valence shells

  16. Atomic Bonds GEOL 131: Minerals – Atoms and Elements

  17. Atomic Bonds GEOL 131: Minerals – Atoms and Elements

  18. Chemical Composition of Minerals GEOL 131: Minerals – Atoms and Elements • Elements present and in what amounts • Well-defined: Limited or no variation • Described by mineral’s formula • Halite (salt): NaCl

  19. Atomic Structure of Minerals GEOL 131: Minerals – Atoms and Elements • Arrangement of atoms • Well-ordered: Repeats in a regular pattern

  20. Atomic Structure of Minerals GEOL 131: Minerals – Atoms and Elements • Arrangement of atoms QUARTZ

  21. Atomic Structure – Diamond vs Graphite GEOL 131: Minerals – Atoms and Elements

  22. Minerals Physical Properties & Identification

  23. GEOL 131: Minerals – Physical Properties & Identification Physical Properties • Each mineral has a unique set of properties • Determined by mineral’s chemical composition and atomic structure • Properties are used to identify unknown minerals

  24. GEOL 131: Minerals – Physical Properties & Identification Physical Properties Commonly Used in Identification • Color • Streak • Luster • Cleavage • Crystal habit • Striations • Hardness • Effervescence • Magnetism

  25. Quartz GEOL 131: Minerals – Physical Properties & Identification COLOR • Easy to observe, but can be misleading • Impurities can produce different colors

  26. GEOL 131: Minerals – Physical Properties & Identification STREAK • Color of powdered mineral • More reliable than “bulk” color Streak plate

  27. GEOL 131: Minerals – Physical Properties & Identification LUSTER • How sample reflects light • Not the same as color NONMETALLIC luster METALLIC luster

  28. GEOL 131: Minerals – Physical Properties & Identification LUSTER • How sample reflects light • Not the same as color Both of these minerals have a METALLIC luster

  29. GEOL 131: Minerals – Physical Properties & Identification CLEAVAGE • How sample cleaves (breaks) • Always the same for a given mineral • Three aspects • Quality • Number of directions • Angle

  30. GEOL 131: Minerals – Physical Properties & Identification CLEAVAGE QUALITY - None No cleavage: irregular breakage surface

  31. GEOL 131: Minerals – Physical Properties & Identification CLEAVAGE QUALITY - Good Note “stair-step” pattern Good cleavage: somewhat regular breakage surface

  32. GEOL 131: Minerals – Physical Properties & Identification CLEAVAGE QUALITY – Excellent/perfect Excellent cleavage: smooth breakage surface

  33. GEOL 131: Minerals – Physical Properties & Identification # OF CLEAVAGE DIRECTIONS • A number • Only applies to good or excellent cleavage quality

  34. GEOL 131: Minerals – Physical Properties & Identification # OF CLEAVAGE DIRECTIONS - One One smooth surface

  35. GEOL 131: Minerals – Physical Properties & Identification # OF CLEAVAGE DIRECTIONS - Two Two non-parallel smooth surfaces

  36. GEOL 131: Minerals – Physical Properties & Identification # OF CLEAVAGE DIRECTIONS - Three Three non-parallel smooth surfaces

  37. GEOL 131: Minerals – Physical Properties & Identification # OF CLEAVAGE DIRECTIONS - Four Fluorite Four non-parallel smooth surfaces

  38. GEOL 131: Minerals – Physical Properties & Identification CLEAVAGE ANGLE • Angle between cleavage surfaces 60-degree angle 90-degree angle 120-degree angle

  39. GEOL 131: Minerals – Physical Properties & Identification CRYSTAL HABIT • How a mineral grows • Unusual to see well-formed crystals in nature • Need space to grow

  40. GEOL 131: Minerals – Physical Properties & Identification CRYSTAL HABIT Well-formed crystal faces Poorly-formed crystals: not enough space

  41. GEOL 131: Minerals – Physical Properties & Identification CRYSTAL HABIT • Don’t confuse a crystal face with an excellent cleavage surface • Crystal face – caused by growth • Cleavage surface – caused by breaking

  42. GEOL 131: Minerals – Physical Properties & Identification STRIATIONS • Thin grooves on mineral’s surface • Can be hard to see From facweb.bhc.edu From www4.uwm.edu

  43. GEOL 131: Minerals – Physical Properties & Identification HARDNESS

  44. GEOL 131: Minerals – Physical Properties & Identification EFFERVESCENCE Dilute hydrochloric acid (HCl) If CO3 ion present, carbon dioxide bubbles will form: CaCO3(calcite) + 2HCl = H2O + CO2 + CaCl2

  45. GEOL 131: Minerals – Physical Properties & Identification MAGNETISM • Some iron-rich minerals are magnetic Magnetite (Fe3O4) attracting a magnet

  46. GEOL 131: Minerals – Physical Properties & Identification MINERAL IDENTIFICATION • Table or flowchart • Observation of unique properties • Narrow down possibilities

  47. GEOL 131: Minerals – Physical Properties & Identification MINERAL IDENTIFICATION

  48. GEOL 131: Minerals – Mineral Groups MINERAL GROUPS • Silicates (largest group) • Carbonates • Sulfates • Sulfides • Oxides • Halides • Native elements

  49. GEOL 131: Minerals – Mineral Groups MINERAL GROUPS - Silicates • Largest group • 90% of Earth’s crust • Si and O atoms in a tetrahedron (pyramid)

  50. GEOL 131: Minerals – Mineral Groups MINERAL GROUPS - Silicates • Oxygen atoms can bond to adjacent tetrahedra in a mineral’s atomic structure • Forms the “backbone” of the mineral • Example: single-chain structure • Each tetrahedron shares two oxygens with adjacent tetrahedra