Earth's Minerals (Book)

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+ What are Minerals?

Physical Properties

The patterns of atoms that make a mineral affect its physical properties. A mineral’s crystal shape is determined by the way the atoms are arranged. For example, you can see how atoms are arranged in halite in Figure above. You can see how salt crystals look under a microscope in Figure below. Salt crystals are all cubes whether they're small or large.

salt crystal image

Under a microscope, salt crystals are cubes.

Other physical properties help scientists identify different minerals. They include:

  • Color: the color of the mineral.
  • Streak: the color of the mineral’s powder.
  • Luster: the way light reflects off the mineral’s surface.
  • Specific gravity: how heavy the mineral is relative to the same volume of water.
  • Cleavage: the mineral’s tendency to break along flat surfaces.
  • Fracture: the pattern in which a mineral breaks.
  • Hardness: what minerals it can scratch and what minerals can scratch it.