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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. ==Common mineraloids== * Amber, non-crystalline structure, organic * 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) * Tektites, meteoritic silica glass 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Mineraloid」の詳細全文を読む スポンサード リンク
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