Supriya Ghosh (Editor)

Mineraloid

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A mineraloid is a mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian is an amorphous glass and not a crystal. Jet is derived from decaying wood under extreme pressure. Opal is another mineraloid because of its non-crystalline nature. Pearl, considered by some to be a mineral because of the presence of calcium carbonate crystals within its structure, would be better considered a mineraloid because the crystals are bonded by an organic material, and there is no definite proportion of the components.

Examples

  • Amber, non-crystalline structure, organic
  • Deweylite, a mixture of serpentine and talc or stevensite
  • Ebonite, vulcanized natural or synthetic rubber (organic); lacks a crystalline structure
  • Jet, non-crystalline nature, organic (very compact coal)
  • Lechatelierite, nearly pure silica glass
  • Limonite, a mixture of oxides and hydroxides of iron
  • Mercury, liquid (IMA/CNMNC valid mineral name)
  • Obsidian, volcanic glass – non-crystalline structure, a glass and quartz mixture
  • Opal, non-crystalline silicon dioxide, a mix of minerals (IMA/CNMNC valid mineral name)
  • Pearl, organically produced carbonate
  • Petroleum, liquid, organic
  • Pyrobitumen, amorphous fossilized petroleum (noncrystalline, organic)
  • Shungite, black, lustrous, more than 98 weight percent of carbon
  • Tektites, meteoritic silica glass

    • References

    Mineraloid Wikipedia
    (Text) CC BY-SA