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 derived from decaying wood under extreme pressure. Opal is another mineraloid because of its non-crystalline nature. Pearl, considered by some to be a mineral because of the presence of calcium carbonate crystals within its 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.

Examples

• Amber, non-crystalline structure, organic
• Ebonite, vulcanized natural or synthetic rubber (organic); lacks a crystalline structure
• Jet, non-crystalline nature, organic (very compact coal)
• Lechatelierite, nearly pure silica glass
• Limonite, a mixture of oxides and hydroxides of iron
• Mercury, liquid (IMA/CNMNC valid mineral name)
• 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, organically produced carbonate
• Petroleum, liquid, organic
• Pyrobitumen, amorphous fossilized petroleum (noncrystalline, organic)
• Tektites, meteoritic silica glass

See also

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

References

• Mineraloids mineraloids are not true minerals