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Geosciences LibreTexts

16.06.01: Chalcedony

  • Page ID
    4102
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    Chalcedony
    Chemical composition Silicon dioxide SiO2
    Crystal system Trigonal
    Habit Aggregate
    Fracture Conchoidal
    Hardness 6.5-7
    Refractive index 1.535 - 1.539
    Specific gravity 2.60
    Lustre Vitreous

    Chalcedony is microcrystalline (cryptocrystalline) quartz. The name is often used to encompass all varieties of microcrystalline quartz such as jasper, carnelian, chrysoprase, and bloodstone. The mineral is very abundant and found all over the world. The most common variety is a muted blue-gray tone (unnamed) found in geodes and vugs.