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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]


See also[edit]

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


  1. ^ Titamgim, Dirk (1988). "Rock Chips: What is a Mineraloid?". Rocks & Minerals. 63 (1): 65. doi:10.1080/00357529.1988.11761818.
  2. ^ 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.
  3. ^ 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.

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