Mineraloid
Encyclopedia
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. Pearl
s, 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.
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
-like substance that does not demonstrate crystallinity
Crystallinity
Crystallinity refers to the degree of structural order in a solid. In a crystal, the atoms or molecules are arranged in a regular, periodic manner. The degree of crystallinity has a big influence on hardness, density, transparency and diffusion. In a gas, the relative positions of the atoms or...
. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian
Obsidian
Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth...
is an amorphous glass
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
and not a crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
. Jet
Jet (lignite)
Jet is a geological material and is considered to be a minor gemstone. Jet is not considered a true mineral, but rather a mineraloid as it has an organic origin, being derived from decaying wood under extreme pressure....
is derived from decaying wood under extreme pressure. Opal
Opal
Opal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. 3% to 21% of the total weight is water, but the content is usually between 6% to 10%. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most...
is another mineraloid because of its non-crystal nature. Pearl
Pearl
A pearl is a hard object produced within the soft tissue of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other...
s, 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.
Common mineraloids
- AmberAmberAmber is fossilized tree resin , which has been appreciated for its color and natural beauty since Neolithic times. Amber is used as an ingredient in perfumes, as a healing agent in folk medicine, and as jewelry. There are five classes of amber, defined on the basis of their chemical constituents...
, non-crystalline structure - JetJet (lignite)Jet is a geological material and is considered to be a minor gemstone. Jet is not considered a true mineral, but rather a mineraloid as it has an organic origin, being derived from decaying wood under extreme pressure....
, non-crystalline nature, very compact coal - Native mercuryMercury (element)Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
, liquid, IMAInternational Mineralogical AssociationThe International Mineralogical Association is an international group of 38 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 4000 plus known mineral species...
/CNMNC valid mineral name - LechatelieriteLechatelieriteLechatelierite is silica glass, amorphous SiO2. One common way in which lechatelierite forms naturally is by very high temperature melting of quartz sand during a lightning strike...
, nearly pure silica glass - LimoniteLimoniteLimonite is an ore consisting in a mixture of hydrated iron oxide-hydroxide of varying composition. The generic formula is frequently written as FeO·nH2O, although this is not entirely accurate as limonite often contains a varying amount of oxide compared to hydroxide.Together with hematite, it has...
, a mixture of oxides - Lapis LazuliLapis lazuliLapis lazuli is a relatively rare semi-precious stone that has been prized since antiquity for its intense blue color....
, a mix of minerals - ObsidianObsidianObsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock.It is produced when felsic lava extruded from a volcano cools rapidly with minimum crystal growth...
, volcanic glass - non-crystalline structure, a glass and quartz mixture - OpalOpalOpal is an amorphous form of silica related to quartz, a mineraloid form, not a mineral. 3% to 21% of the total weight is water, but the content is usually between 6% to 10%. It is deposited at a relatively low temperature and may occur in the fissures of almost any kind of rock, being most...
, non-crystalline silicon dioxideSilicon dioxideThe chemical compound silicon dioxide, also known as silica , is an oxide of silicon with the chemical formula '. It has been known for its hardness since antiquity...
, a mix of minerals, IMA/CNMNC valid mineral name - PearlPearlA pearl is a hard object produced within the soft tissue of a living shelled mollusk. Just like the shell of a mollusk, a pearl is made up of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. The ideal pearl is perfectly round and smooth, but many other...
, organicly produced carbonate - PetroleumPetroleumPetroleum or crude oil is a naturally occurring, flammable liquid consisting of a complex mixture of hydrocarbons of various molecular weights and other liquid organic compounds, that are found in geologic formations beneath the Earth's surface. Petroleum is recovered mostly through oil drilling...
, liquid - Pyrobitumen, non-homogeneous, non-crystalline structure, doesn't melt by heating
- VulcaniteEboniteEbonite is a brand name for very hard rubber first obtained by Charles Goodyear by vulcanizing rubber for prolonged periods. It is about 30% to 40% sulfur. Its name comes from its intended use as an artificial substitute for ebony wood...
, vulcanizeVulcanizationVulcanization or vulcanisation is a chemical process for converting rubber or related polymers into more durable materials via the addition of sulfur or other equivalent "curatives." These additives modify the polymer by forming crosslinks between individual polymer chains. Vulcanized material is...
d natural or synthetic rubber, thus not a mineral due lack of crystalline structure - Tektites, meteoritic silica glass
See also
- List of minerals - Mineraloids are listed after minerals in each alphabetically sorted section.
- NonmineralNonmineralA nonmineral is a substance found in a natural environment that does not satisfy the definition of a mineral and is not even a mineraloid...