Mineraloid

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 due to its non-crystal nature. Pearls, considered by some to be a mineral due to 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.

Related Topics:
Mineral - Obsidian - Amorphous - Glass - Crystal - Jet - Coal - Opal - Pearl

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Other naturally occurring substances that appear superficially to be minerals in nature are Nonminerals.

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