A mineraloid is a naturally occurring

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

-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 Glass is a non- crystalline, often transparent, amorphous solid that has widespread practical, technological, and decorative use in, for example, window panes, tableware, and optics. Glass is most often formed by rapid cooling (quenchin ...

and not a

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

. Jet is derived from decaying wood under extreme pressure.

Opal Opal is a hydrated amorphous form of silica (SiO2·''n''H2O); its water content may range from 3 to 21% by weight, but is usually between 6 and 10%. Due to its amorphous property, it is classified as a mineraloid, unlike crystalline form ...

is another mineraloid because of its non-crystalline nature.

Pearl A pearl is a hard, glistening object produced within the soft tissue (specifically the mantle) of a living shelled mollusk or another animal, such as fossil conulariids. Just like the shell of a mollusk, a pearl is composed of calcium carb ...

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.

Examples

* Allophane, solid (IMA/CNMNC valid mineral name) *

Amber Amber is fossilized tree resin that has been appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects."Amber" (2004). In M ...

, non-crystalline structure, organic * Anthracite or hard coal * Bituminous coal * Chlorophaeite * Chrysocolla, solid (IMA/CNMNC valid mineral name) * Deweylite, a mixture of serpentine and talc or stevensite * Diatomite * 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) * Leonardite * Libyan desert glass *

Lignite Lignite, often referred to as brown coal, is a soft, brown, combustible, sedimentary rock formed from naturally compressed peat. It has a carbon content around 25–35%, and is considered the lowest rank of coal due to its relatively low heat ...

, or brown coal * Limonite, a mixture of oxides and hydroxides of iron * Moldavite * Mookaite/Radiolarite * Obsidian, volcanic glass – non-crystalline structure, a silica rich glass *

, non-crystalline hydrated silica silicon dioxide, solid (IMA/CNMNC valid mineral name) *

Ozokerite Ozokerite or ozocerite, archaically referred to as earthwax or earth wax, is a naturally occurring odoriferous mineral wax or paraffin found in many localities. Lacking a definite composition and crystalline structure, it is not considered a min ...

, a black waxy hydrocarbon mixture *

Palagonite Palagonite is an alteration product from the interaction of water with volcanic glass of chemical composition similar to basalt. Palagonite can also result from the interaction between water and basalt melt. The water flashes to steam on contact ...

, organically produced carbonate * Pele's hair *

Petroleum Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...

, liquid, organic *

Psilomelane Psilomelane is a group name for hard black manganese oxides including hollandite and romanechite. Psilomelane consists of hydrous manganese oxide with variable amounts of barium and potassium. Psilomelane is erroneously, and uncommonly, known ...

Pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular v ...

* Pyrobitumen, amorphous fossilized petroleum (noncrystalline, organic) * Shungite, black, lustrous, more than 98

weight percent In chemistry, the mass fraction of a substance within a mixture is the ratio w_i (alternatively denoted Y_i) of the mass m_i of that substance to the total mass m_\text of the mixture. Expressed as a formula, the mass fraction is: : w_i = \frac ...

of carbon * Sideromelane, volcanic glass – non-crystalline, an iron rich, silica poor glass * Tektite, meteoritic silica rich glass *

Water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...

, e. g. as inclusions in other crystals, liquid * Zietrisikite, a mineral hydrocarbon wax

References

External links

The Mineraloids Class
Amethyst Galleries. Mineralogy {{Mineral-stub de:Mineraloid he:מינרל#מינרלואידים

Examples

See also

References

External links