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The Earths Crust #2 Mineral Identification
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The Earths Crust #2 Mineral Identification


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    • 1. The Earth’s Crust Mineral Identification
    • 2. Mineral Identification
      • What differences can you see between these minerals that could help identify them?
      • What properties could be used to identify minerals?
    • 3.
      • There are six main characteristics that we will use to identify minerals:
              • 1. colour
              • 2. crystals (the shape of)
              • 3. hardness
              • 4. streak
              • 5. cleavage and fracture
              • 6. luster
              • Cadburys chocolate hardly stays creamy for long
    • 4. 1. Colour
      • Colour - It's pretty easy to tell the colour of a mineral and it can give a clue to the identity of the mineral.
      • However, colour alone cannot identify a mineral. For example, pyrite (fools gold) and gold are both the same colour.
    • 5.
      • In addition, a mineral can come in more than one colour.
      • For example, the mineral corundum can occur in several different colours due to impurities.
      • Corundum is better known as amethyst (purple), emerald (green), topaz (yellow), and ruby (red).
      • In its pure form, corundum is white.
    • 6. 2. Crystals
      • Crystal shape – Minerals sometimes occur as crystals. A crystal occurs naturally and has straight edges, flat sides, and regular angles.
      • Each mineral forms a specific shape of crystal so it can be used for identification purposes.
    • 7. 3. Hardness
      • Hardness – the hardness of a mineral can be measured and compared to other minerals using the Moh’s Hardness Scale .
      • The scale goes from one (the softest) to 10 (the hardest) and ranks minerals on their “scratchability”
      10 (hardest) diamond Emery paper (9.0) 9 corundum Sandpaper (7.5) 8 topaz Streak plate (7) 7 quartz Steel file (6.5) 6 feldspar Glass (5.5) 5 apatite Iron nail (4.5) 4 fluorite Copper penny (3.5) 3 calcite Fingernail (2.5) 2 gypsum Soft pencil point (1.5) 1 (softest) talc Hardness of Common Items Mineral Hardness Mineral
    • 8. 4. Streak
      • Streak – the colour a mineral leaves behind when it is rubbed on a hard surface (usually a streak plate)
      • Often the colour a mineral leaves behind is different from the colour of the mineral.
    • 9. 5. Cleavage and Fracture
      • Cleavage and Fracture – Describes how a mineral breaks apart
    • 10.
      • The way a mineral breaks apart can be a clue to its identity.
      • If it breaks along smooth, flat surfaces, or planes, it is said to have cleavage .
      • e.g. calcite or mica - Mica can be pulled apart into thin, flat, sheets and Halite forms flat edges when broken.
    • 11.
      • If it breaks with rough or jagged edges, it is said to have fracture. E.g. obsidian
      • Obsidian fractures when broken apart leaving rough, jagged edges.
    • 12.  
    • 13. 6. Lustre
      • Lustre – the way a mineral reflects light
      • The "shininess," or lustre of a mineral depends on how light is reflected from its surface.
    • 14.
      • The surface of a mineral can reflect light in many different ways including:
      • 1. Metallic Lustre - the mineral reflects light like a polished piece of metal.
    • 15.
      • 2. Vitreous Lustre (Glassy) - the mineral reflects light like a piece of glass when it is tilted from side to side.
    • 16.
      • 3. Pearly Lustre - the mineral reflects light like a pearl.
    • 17.
      • 4. Dull Lustre - the mineral scatters the light and will not appear shiny at all.