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-crystal nature. Pearls, considered by some to be a mineral because of 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.
- Amber, non-crystalline structure
- Jet, non-crystalline nature, very compact coal
- Native mercury, liquid, IMA/CNMNC valid mineral name
- Lechatelierite, nearly pure silica glass
- Limonite, a mixture of oxides
- Lapis Lazuli, a mix of minerals
- 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, organicly produced carbonate
- Petroleum, liquid
- Pyrobitumen, non-homogeneous, non-crystalline structure, doesn't melt by heating
- Vulcanite, vulcanized natural or synthetic rubber, thus not a mineral due lack of crystalline structure
- Tektites, meteoritic silica glass
- List of minerals - Mineraloids are listed after minerals in each alphabetically sorted section.
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