Colored Stones: Crystal Systems and Gem Identification
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Questions and Answers

What is the primary factor that determines a gem's density and specific gravity?

  • The presence of inclusions
  • The gem's color
  • The types of atoms it's made of, and how closely they're packed together (correct)
  • Its crystal structure

    • What can the exterior shape of a crystal indicate?

  • Its symmetry at an atomic level (correct)
  • Its crystal structure
  • Its chemical composition
  • Its optical properties

    • Why are some gems rare?

  • Because they are highly prized by collectors
  • Because they are too small to be valuable
  • Because they are easily synthesized
  • Because they require rare chemical elements or unique geological conditions to form (correct)

    • What is twinning the result of?

    <p>A change during crystal growth, or from cooling or pressure after the crystal has grown (D)</p> Signup and view all the answers

    What can inclusions in a colored stone help identify?

    <p>Whether the stone is natural or manmade, untreated or treated (A)</p> Signup and view all the answers

    What determines a gem's reaction to external stress?

    <p>Its crystal structure (A)</p> Signup and view all the answers

    Study Notes

    Crystal Systems and Identification

    • Crystalline minerals are classified into 7 crystal systems based on the symmetry of their unit cells.
    • Recognizable crystal shapes of rough gemstones can help identify them.
    • The exterior shape of a crystal often indicates its symmetry at an atomic level.

    Factors Affecting Gemstone Shapes and Sizes

    • Shapes and sizes of rough gem crystals affect the shapes and sizes of finished stones.
    • Rarity of gems is due to the requirement of rare chemical elements or unique geological conditions, or both, to form.

    Physical Properties of Gems

    • A gem's density and specific gravity depend on the types of atoms it's made of, and how closely they're packed together.
    • Twinning can occur due to a change during crystal growth, or from cooling or pressure after the crystal has grown.

    Fracture and Inclusions

    • Different ways a gem breaks are called cleavage, parting, and fracture.
    • Inclusions in a colored stone can help identify it as natural or man-made, untreated or treated.
    • A gem's crystal structure determines its reaction to external stress.
    • Large inclusions can dramatically affect beauty, value, and durability.

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    Related Documents

    Colored Stones 3 Physical Properties PDF

    Description

    Learn about the classification of crystalline minerals into seven crystal systems and how the exterior shape of a crystal indicates its symmetry. Discover how the shapes and sizes of rough gem crystals affect the finished stones.

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