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Definition of a mineral:
Naturally occurring
Inorganic solid
Ordered internal molecular structure
Definite chemical composition

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  • Hematite can be brown, black, metallic gray and earthy but in all cases it gives a red-brown streak.
  • Mineral

    1. 1. MineralsBy : Kornelis Eko Patty
    2. 2. Chapter 2 Opening Figure
    3. 3. Figure 2.1
    4. 4. Minerals: Building blocks of rocks• Definition of a mineral: • Naturally occurring • Inorganic solid • Ordered internal molecular structure • Definite chemical composition• Definition of a rock: • A solid aggregate or mass of minerals
    5. 5. Physical properties of minerals• Crystal Form • External expression of the orderly internal arrangement of atoms • Crystal growth is often interrupted because of competition for space and rapid loss of heat
    6. 6. Figure 2.2
    7. 7. The mineral quartz oftenexhibits good crystal formCopyright © 2006 Pearson Prentice Hall, Inc.
    8. 8. LUSTER – Does this look like it could be made from a hard metal?• Describes how light reflects off the surface• Categories: Metallic or Non-metallicMetallic – luster of metal – shines like a hard metal (light does not penetrate)Many non-metallic minerals are SHINY because they are transparent or semi-transparent• Non-metallic: vitreous or glassy; silky; pearly; greasy; waxy, dull; earthy
    9. 9. Pyrite (fool’s gold) displays metallic luster Copyright © 2006 Pearson Prentice Hall, Inc.
    10. 10. Examples of metallic luster
    11. 11. More Examples of Metallic Luster PYRITEPyrite (FeS2)Galena (PbS) GALENA
    12. 12. Example of non-metallic luster• Vitreous--quartz
    13. 13. Example of non-metallic luster• Silky--example plagioclase feldspar
    14. 14. Non-metallic and metallic luster –earthy hematite – metallic hematite
    15. 15. Physical properties of minerals• Color • Generally an unreliable diagnostic property to use for mineral identification • Often highly variable for a given mineral due to slight changes in mineral chemistry • Exotic colorations of some minerals produce gemstones
    16. 16. Quartz (SiO2) exhibits a variety of colors Citrine Smoky QuartzAmethyst
    17. 17. Some Colors of Quartz
    18. 18. Physical properties of minerals• Streak • Color of a mineral in its powdered form • Helpful in distinguishing different forms of the same mineral• Hardness • Resistance of a mineral to abrasion or scratching • All minerals are compared to a standard scale called the Mohs scale of hardness
    19. 19. Streak – the color ofa powdered mineral
    20. 20. STREAK• For opaque minerals, if you rub the sample across a streak plate, it will leave a colored powder. This streak is distinctive for minerals and is used to identify minerals.
    21. 21. Varieties of Hematite – all same color streak
    22. 22. Mohs scale of hardness HARDNESS – Mineral’s resistance to scratching or abrasion. Minerals with higher numbers will scratch minerals beside
    23. 23. Physical properties of minerals• Cleavage • Tendency to break along planes of weak bonding • Produces flat, shiny surfaces • Described by resulting geometric shapes – Number of planes – Angles between adjacent planes
    24. 24. Commoncleavagedirections Figure 2.13
    25. 25. Three examples of perfect cleavage – fluorite, halite, and calcite Copyright © 2006 Pearson Prentice Hall, Inc.
    26. 26. Cleavage – due to weak bonds in the crystal structureHalite (NaCl)Fluorite (CaF2) HALITE FLUORITE
    27. 27. Cleavage MUSCOVITE BIOTITE
    28. 28. Physical properties of minerals• Fracture • Absence of cleavage when a mineral is broken• Specific Gravity • Ratio of the weight of a mineral to the weight of an equal volume of water • Average value is approximately 2.7
    29. 29. Conchoidal fracture
    30. 30. Rose Quartz – Conchoidal Fracture
    31. 31. Conchoidal Fracture - Quartz Obsidian
    32. 32. Density (Specific Gravity)• All minerals have density (mass / volume), but some are very dense• Examples include galena, magnetite, and gold• Specific Gravity is the density of the mineral compared with density of water http://www.minerals.net/mineral/elements/gold/gold1.htm
    33. 33. Physical properties of minerals• Other properties • Magnetism • Reaction to hydrochloric acid • Malleability • Double refraction • Taste • Smell • Elasticity • Striations
    34. 34. Other Properties• Magnetism - Property of a substance such that it will spontaneous orient itself within a magnetic field. Magnetite (Fe3O4) has this property and it can be used to distinguish it from other non-magnetite iron oxides, such as hematite (Fe2O3).• Straitions - Commonly found on plagioclase feldspar. Straight, parallel lines on one or more of the cleavage planes caused by mineral twinning.• Double Refraction - Seen in calcite crystals. Light is split or refracted into two components giving rise to two distinct images.
    35. 35. Special Characteristics-- Magnetism • Many iron minerals will produce an invisible magnetic force field • “Lodestone” was used by Vikings more than 1,000 years ago as compasseshttp://www.minerals.net/mineral/oxides/magnetit/magneti4.htm
    36. 36. Acid Test for Carbonates• Special Characteristics: Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas)
    37. 37. Special Characteristics-- Fluorescence • Some minerals will glow when placed under short-wave or long-wave ultraviolet rays • Franklin and Ogdensburg NJ are famous for their fluorescent mineralshttp://www.sterlinghill.org/Tour%20information.htm
    38. 38. Special Characteristics-- Salty Taste• DO NOT TASTE MOST MINERALS!• Halite is the exception--it will taste saltyhttp://mineral.galleries.com/scripts/item.exe?LIST+Minerals+Halides+Halite
    39. 39. Classification of Minerals• Over 4000 minerals identified.• Classification based on the key ion or element that makes up the “building block” of the mineral.• An ion is an atom or molecule with an unbalanced electrical charge.• Most important group is the Silicate Minerals, which form the majority of the rock-forming minerals.
    40. 40. Classification of MineralsRock-forming minerals • Common minerals that make up most of the rocks of Earth’s crust • Only a few dozen members • Composed mainly of the 8 elements that make up over 98% of the continental crust
    41. 41. Elemental abundances in continental crust Figure 2.15
    42. 42. Classification of Minerals• Silicates • Most important mineral group – Comprise most of the rock-forming minerals – Very abundant due to large amounts of silicon and oxygen in Earth’s crust • Basic building block is the silicate ion (aka the silicon-oxygen tetrahedron) – Four oxygen ions surrounding a much smaller silicon ion
    43. 43. Twoillustrations of the Silicate ion Figure 2.16
    44. 44. Classification of Minerals• Silicate structures • Single silicate ions are linked together to form various structures including – Isolated ions – Ring structures – Single and double chain structures – Sheet or layered structures – Complex 3-dimensional structures
    45. 45. Classification of Minerals• Common Silicate minerals • Olivine – High temperature Fe-Mg silicate – Individual silicate linked together by iron and magnesium ions – Forms small, rounded crystals with no cleavage
    46. 46. Figure 2.19a
    47. 47. Classification of Minerals• Common Silicate minerals • Pyroxene Group – Single chain structures involving iron and magnesium – Two distinctive cleavages at nearly 90 degrees – Augite is the most common mineral in the pyroxene group
    48. 48. Figure 2.19b
    49. 49. Classification of Minerals• Common Silicate minerals • Amphibole Group – Double chain structures involving a variety of ions linking the silicate ion – Two perfect cleavages at non right angles Hornblende is the most common mineral in the amphibole group
    50. 50. Figure 2.19c
    51. 51. Classification of Minerals• Common Silicate minerals • Mica Group – Sheet structures that result in one direction of perfect cleavage – Biotite is the common dark colored mica mineral – Muscovite is the common light colored mica mineral
    52. 52. Figure 2.19d
    53. 53. Figure 2.19e
    54. 54. Classification of Minerals• Common Silicate minerals • Feldspar Group – Most common mineral group – 3-dimensional framework that exhibits two directions of cleavage at 90 degrees – Orthoclase (potassium feldspar) and Plagioclase (sodium and calcium feldspar) are the two most common members
    55. 55. Figure 2.19f
    56. 56. Potassium feldsparCopyright © 2006 Pearson Prentice Hall, Inc. Figure 2.19 F
    57. 57. Plagioclase feldspar Figure 2.20
    58. 58. Classification of Minerals• Common Silicate minerals • Quartz – Consists entirely of silicon and oxygen (SiO2). This is a material called silica. – Strong bonds in all directions – cleavage absent. – Naturally clear, but impurities cause colors.
    59. 59. Figure 2.19g
    60. 60. Classification of Minerals• Important nonsilicate minerals • Several major groups exist including – Oxides – Sulfides – Sulfates – Native Elements – Carbonates – Halides – Phosphates
    61. 61. Classification of Minerals• Important nonsilicate minerals • Carbonates Primary constituents in limestone; an abundant marine sedimentary rock. Calcite (calcium carbonate) and Dolomite (calcium-magnesium carbonate) are the two most important carbonate minerals.