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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 a dense form of coal. Opal is another mineraloid because of its non-crystal nature. Pearls, considered by some to be a mineral because of the presence of calcium carbonate crystals within their 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.

Common Mineraloids

  • Amber, organic, non-crystal structure.
  • Anthracite, a variety of coal, "hard coal."
  • Coal, organic, nonhomogeneous, and non-crystal structure.
  • Jet, not considered a true mineral due to organic, non-crystal nature, a mineraloid.
  • Lignite, a variety of coal, "Brown coal."
  • Limonite, amorphous hydrated iron oxide, a mineraloid.
  • Obsidian, volcanic glass - non-crystal structure.
  • Opal, non-crystal structure, a mineraloid.
  • Pearl, often considered a mineral due to crystal components, but then not a mineral due to organic origin, probably should be a mineraloid.
  • Petroleum, organic and liquid.
  • pyrobitumen, organic, nonhomogeous, non-crystal structure.
  • Vulcanite, vulcanized natural or synthetic rubber, thus not a mineral due to organic composition, lack of crystal structure, and not naturally occurring.

See also

  • List of minerals Mineraloids are listed after minerals in each alphabetically sorted section.
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Mineraloid". A list of authors is available in Wikipedia.
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