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 is considered a mineraloid because the included calcite and/or aragonite crystals are bonded by an organic material, and there is no definite proportion of the components.
- Allophane, solid (IMA/CNMNC valid mineral name)
- Amber, non-crystalline structure, organic
- Anthracite or hard coal
- Bituminous coal
- Chrysocolla, solid (IMA/CNMNC valid mineral name)
- Deweylite, a mixture of serpentine and talc or stevensite
- Ebonite, 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)
- Libyan desert glass
- Lignite, or brown coal
- Limonite, a mixture of oxides and hydroxides of iron
- 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
- Pearl, organically produced carbonate
- Pele's hair
- Petroleum, liquid, organic
- Pyrobitumen, amorphous fossilized petroleum (noncrystalline, organic)
- Shungite, black, lustrous, more than 98 weight percent of carbon
- Sideromelane, volcanic glass – non-crystalline, an iron rich, silica poor glass
- Tektite, meteoritic silica rich glass
- Water, e. g. as inclusions in other crystals, liquid
- Zietrisikite, a mineral hydrocarbon wax
- List of minerals – Mineraloids are listed after minerals in each alphabetically sorted section.
- 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.
- The Mineraloids Class. Amethyst Galleries.