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Geosciences LibreTexts

16.37: Obsidian

  • Page ID
    4721
  • Obsidian (named after the roman, Obsius) is a volcanic glass.

    Diagnostics

    Color

    Its color is black, grey, brown, green and can be gold or silver due to inclusions.

    Diaphaneity

    Transparent to opaque.

    Hardness

    Obsidian has a hardness of 5-5 1/2.

    Specific gravity

    Obsidian has a density of 2.35-2.60.

    Refractive index

    Obsidian is singly refractive with an R.I. range of 1.45 to 1.55.

    Varieties

    • Snowflake obsidian is the trade name for an obsidian with grey-white, ball shaped inclusions of Spherulites found in Mexico and the United States.

    Localities

    Deposits are found in the United States, Mexico, Japan, Italy, Iceland, Indonesia, and Equador.