A mineraloid is a naturally-occurring 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^[who?] 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[edit]

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  Amber, non-crystalline structure, organic


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  Chlorophaeite^[1]


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  Deweylite, a mixture of serpentine and talc or stevensite^[2]


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  Ebonite, vulcanized natural or synthetic rubber (organic); lacks a crystalline structure


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  Jet, non-crystalline nature, organic (very compact coal)


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  Lechatelierite, nearly pure silica glass


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  Limonite, a mixture of oxides and hydroxides of iron


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  Mercury, liquid (IMA/CNMNC valid mineral name)


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  Obsidian, volcanic glass – non-crystalline structure, a silica rich glass


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  Opal, non-crystalline hydrated silica silicon dioxide (IMA/CNMNC valid mineral name)


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  Palagonite^[1]


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  Pearl, organically produced carbonate


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  Petroleum, liquid, organic


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  Pyrobitumen, amorphous fossilized petroleum (noncrystalline, organic)


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  Sideromelane^[1]


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  Shungite, black, lustrous, more than 98 weight per cent of carbon


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  Tektites, meteoritic silica rich glass

See also[edit]

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  List of minerals – Mineraloids are listed after minerals in each alphabetically sorted section.

References[edit]

External links[edit]

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  The Mineraloids Class. Amethyst Galleries.

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