Coals are usually thought of as black or dark brown rocks consisting mainly of carbonized plant matter.
Types of coal include: "bituminous, anthracite, or lignite, and grades and varieties thereof."
Coal is mostly carbon with variable amounts of other elements; chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is composed of macerals, minerals and water. Fossils and amber may be found in coal.
An organic mineral appears to be a naturally occurring mineral containing one or more organic chemicals at a concentration of greater than 25 molecular %.
Def. a "rare white monoclinic organic mineral, 7-isopropyl-1,4a-dimethyl-dodecahydro-1H-phenanthrene [C19H34], found in fossilized wood" is called a fichtelite.
Also, occurs in "fossilized pine wood from a peat bog; in organic-rich modern marine sediment."
Def. an "orthorhombic-dipyramidal white mineral containing carbon and hydrogen [C19H24]" is called a simonellite.
Def. a "rare organic mineral [C14H10 or (C6H4)2CH2, a polymorph of fluorene], an orthorhombic hydrocarbon formed by combustion of coal or pyritic black shale deposits"
Kratochvilites have about 58.3 at % carbon.
Def. a "soft, orthorhombic hydrocarbon [C22H14] mineral, usually greenish-yellow to light brown in colour with bluish fluorescence" is called an idrialite.
Def. a solid, homogeneous, monoclinic (space group P2/c, no. 13, or P21/c, no. 14), naturally occurring, chemical compound with the formula C24H12 that results from natural inorganic processes is called a carpathite.
Def. a "rare hydrocarbon mineral composed of coronene" is called a carpathite.
"Carpathite (aka Karpatite) is a very rare organic species, being a polycyclic aromatic hydrocarbon (PAH). This striking specimen from the old Picacho Mercury Mine of California features a very interesting radial spray of highly lustrous, canary-yellow carpathite lathes to 2.0 cm on starkly contrasting, sparkly, drusy quartz."
Def. a "black rock formed from prehistoric plant remains, composed largely of carbon and burned as a fuel" is called a coal.
Def. the process by which plant remains become coal is called coalification.
The chart on the right is an idealized classification of coals from peat through anthracite using total water content (%), energy content (kJ/Kg), volatiles, and surface reflectivity.
Coal is formed if dead plant matter decays into peat and over millions of years the heat and pressure of deep burial converts the peat into coal.
Coalification starts with dead plant matter decaying into peat; then over millions of years the heat and pressure of deep burial causes the loss of water, methane and carbon dioxide and an increase in the proportion of carbon. Thus first lignite (also called "brown coal"), then sub-bituminous coal, bituminous coal, and lastly anthracite (also called "hard coal" or "black coal") may be formed.
Def. a mixture of gases (chiefly hydrogen, methane, and carbon monoxide) obtained by the destructive distillation of coal, or gas given off when coal is burned, is called coal gas.
Def. a "flammable liquid ranging in color from clear to very dark brown and black, consisting mainly of hydrocarbons, occurring naturally in deposits under the Earth's surface" is called a petroleum.
Def. a "black, oily, sticky, viscous substance, consisting mainly of hydrocarbons derived from organic materials such as wood, peat, or coal" is called a tar.
Def. a thick black liquid produced by the destructive distillation of bituminous coal is called a coal tar.
It contains at least benzene, naphthalene, phenols, and aniline.
Def. any "of a wide variety of aliphatic or aromatic liquid hydrocarbon mixtures distilled from petroleum or coal tar" is called a naphtha.
Def. a black viscid substance intermediate between petroleum and asphalt is called a maltha, or malthite.
Def. a black viscous mixture of hydrocarbons obtained naturally is called a bitumen.
In the image on the right, bitumen occurs with lussatite, an opal.
Def. a "dark, extremely viscous material remaining in still after distilling crude oil and tar" is called a pitch.
Def. a "sticky, black and highly viscous liquid or semi-solid, composed almost entirely of bitumen, that is present in most crude petroleums and in some natural deposits" is called an asphalt.
Def. a natural, waxy hydrocarbon mineraloid is called a zietrisikite.
Def. a "hard, generally yellow to brown translucent fossil resin" is called an amber.
Def. soil "formed of dead but not fully decayed plants found in bog areas" is called peat.
Def. a brown, soil-like material characteristic of boggy, acid ground, consisting of partly decomposed vegetable matter, is called a peat.
Def. a "low-grade, brownish-black coal" is called a lignite.
Def. a "hard, black form of coal", specifically lignite is called a jet.
Def. a "form of carbonized ancient plants; the hardest and cleanest-burning of all the coals; hard coal" is called anthracite.
Def. a coal of a hard variety that contains relatively pure carbon is called an anthracite.
Def. a solid "residue from roasting coal" is called a coke.
Neuropteris, a fern, leaf impressions and fossils occur in bituminous coal such as in the image on the right. These coal seams and strata are dated to the Carboniferous period.
The Lepidodendrales, quillwort-like large tree-like plants from the Carboniferous also left fossils in bituminous coal as on the left.
A rocky object is any object, including astronomical objects, composed of one or more types of rocks.
Def. a "nodule of plant material permeated with minerals found mostly in bituminous and anthracite coal seams" is called a coal ball.
Def. a "stratum of coal between strata of other rocks" is called a coal seam.
Both the Paleocene and Eocene of the Tertiary have coal seams in their stratigraphy, shown in the image on the right, of the Powder River Basin.
On the left is an image of coal seams in the strata of Roome Bay, Scotland.
The Tertiary Period extends from 65.5 ± 0.3 to 2.588 ± 0.005 x 106 b2k.
The Yellowstone Basin in the lower Tertiary has coal seams such as the one imaged on the right, about 8 m thick.
"The Cretaceous period is the third and final period in the Mesozoic Era. It began 145.5 million years ago after the Jurassic Period and ended 65.5 million years ago, before the Paleogene Period of the Cenozoic Era."
The Pine Ridge section of the Late Cretaceous on the right contains coal seams.
The second image on the right exhibits an anthracite coal seam between Cretaceous sandstone strata from Central Utah, USA.
Def. a series of strata of the Carboniferous period, including coal seams, is called coal measures.
Def. an extensive area containing a number of underground coal deposits is called a coalfield.
Def. land consisting largely of beat or peat bogs is called a peatland.
- There is at least one coal seam in each geologic period.
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