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A mineraloid is a naturally occurring substance that resembles a mineral, but does not demonstrate the crystallinity of a mineral. Mineraloid substances possess chemical compositions that vary beyond the generally accepted ranges for specific minerals, for example, obsidian is an amorphous glass and not a true crystal; lignite (jet) is derived from the decay of wood under extreme pressure underground; and opal is a mineraloid substance because of its non-crystalline nature. Pearl is a mineraloid substance because the calcite crystals and the aragonite crystals are bonded by an organic material, and naturally occurs without definite proportions of the components.

The first usage of the term mineraloid substance was in 1909, by mineralogist and geologist Julian Niedzwiedzki, in identifying and describing amorphous substances that resemble minerals.^[1]

Examples

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Allophane, solid (IMA/CNMNC valid mineral name)
Amber, non-crystalline structure, organic
Anthracite or hard coal
Bituminous coal
Chlorophaeite^[2]
Chrysocolla, solid (IMA/CNMNC valid mineral name)
Deweylite, a mixture of serpentine and talc or stevensite^[3]
Diatomite
Ebonite,^{[citation needed]} vulcanized natural or synthetic rubber (organic); lacks a crystalline structure
Fulgurite, a variety of the mineraloid lechatelierite
Jet, non-crystalline nature, organic (very compact coal)
Lechatelierite, nearly pure silica glass, solid (IMA/CNMNC valid mineral name)
Leonardite
Libyan desert glass
Lignite—brown coal
Limonite, a mixture of oxides and hydroxides of iron
Mercury, (as liquid)
Moldavite
Mookaite/Radiolarite
Obsidian—volcanic glass; non-crystalline structure, a silica rich glass
Opal, non-crystalline hydrated silica silicon dioxide, solid (IMA/CNMNC valid mineral name)
Ozokerite, a black waxy hydrocarbon mixture
Palagonite^[2]
Pearl, organically produced carbonate
Pele's hair
Petroleum, liquid, organic
Psilomelane
Pumice
Pyrobitumen, amorphous fossilized petroleum (noncrystalline, organic)
Shungite, black, lustrous, more than 98 weight percent of carbon
Sideromelane,^[2] volcanic glass – non-crystalline, an iron rich, silica poor glass
Tektite, meteoritic silica rich glass
Water, e.g. as inclusions in other crystals, or in the form of rain, (as liquid)
Zietrisikite, a mineral hydrocarbon wax

References

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^ Titamgim, Dirk (1988). "Rock Chips: What is a Mineraloid?". Rocks & Minerals. 63 (1): 65. doi:10.1080/00357529.1988.11761818.
^ ^a ^b ^c Peacock, M. A.; Fuller, R. E. (1928). "Chlorophaeite, sideromelane, and palagonite from the Columbia River Plateau" (PDF). American Mineralogist. 13: 360–382. Retrieved 6 September 2017.
^ Schandl, Eva S.; Gorton, Michael P. (1995). "Phyllosilicate Alteration of Olivine in The Lower Sheeted Dike Complex, Leg 140, Hole 504B" (PDF). Proceedings of the Ocean Drilling Program, Scientific Results. Proceedings of the Ocean Drilling Program. 137/140: 207–216. doi:10.2973/odp.proc.sr.137140.019.1995. ISSN 1096-7451.

External links

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The Mineraloids Class. Amethyst Galleries.

Examples

See also

References

External links