Rocks of chemical and organic origin. Rock classification

ORGANIC ROCKS (from the Greek organon - organ and -genes - giving birth, born, biogenic rocks * a. organogenic rocks, biogenic rocks; and. organogene Gesteine; f. roches organogenes, roches biogenes; I. rocas organogenicas) - sedimentary rocks consisting of the remains of animals and plants and their metabolic products. Organisms have the ability to concentrate certain substances that do not reach saturation in natural waters, forming skeletons or tissues that are preserved in a fossil state.

According to the material composition, carbonate, siliceous, and some phosphate rocks, as well as coals (see), oil shale, oil, and solid bitumen, can be distinguished among organogenic rocks. Organogenic carbonate rocks () consist of shells of foraminifers, corals, bryozoans, brachiopods, mollusks, algae and other organisms.

Their peculiar representatives are reef limestones that make up atolls, barrier reefs and others, as well as writing chalk. Siliceous organogenic rocks include: diatomite, spongolite, radiolarite, etc. Diatomites consist of opal skeletons of diatoms, as well as spicules of flint sponges and radiolarians. Spongolites are rocks containing usually more than 50% spicules of flint sponges. Their cement is siliceous, of opal rounded bodies, or clayey, slightly calcareous, often including secondary chalcedony. Radiolarites are siliceous rocks, more than 50% consisting of radiolarian skeletons, which form radiolarian silt in modern oceans. In addition to radiolarians, they include sponge spicules, rare diatom shells, coccolithophores, and opal and clay particles. Many jaspers have a base of radiolarians.

Phosphate organogenic rocks are not widely distributed. These include shell rocks from phosphate shells of Silurian brachiopods - obolid, accumulations of bones of fossil vertebrates (bone breccias), known in sediments different ages, as well as guano. Organogenic carbonaceous rocks - fossil coals and oil shale - are common, but their mass in the earth's crust is small compared to carbonate rocks. Oil and solid bitumen are peculiar rocks, the main material for the formation of which was phytoplankton.

According to the conditions of formation (mainly in relation to carbonate rocks), bioherms can be distinguished - the accumulation of the remains of organisms in their lifetime, thanato- and taphrocenoses - the joint burial of dead organisms that lived here or were carried by waves and currents; rocks that have arisen from planktonic organisms are called planktonic (for example, diatomite, chalk, foraminiferal limestone).

If organic remains are crushed as a result of the action of waves and surf, organogenic-clastic rocks are formed, consisting of fragments (detritus) of shells and skeletons held together by some mineral substance (for example,).

stones organic origin- selection of stones, photos, properties, origin

Stones born of life

They say about the stone "cold", "dead", "lifeless". But life on Earth is not much younger than the planet itself, and many terrestrial minerals are formed by living organisms. Oil, by modern ideas, there is a visible trace of the existence of microscopic unicellular plants and animals of the distant past. Coal was considered by ancient naturalists to be the brother of oil. Chalk, limestone, marble are the life products of sea creatures...

This is where the list of minerals of biogenic origin that comes to mind to the average person usually ends. However, a knowledgeable mineralogist could go on and on with the list of rocks that appeared on Earth solely due to the existence of life.

Even gemology, the science of precious stones, is ready to present an impressive list of gems, each of which was once alive. The champion of popularity among jewelry of biological nature is pearls!

Mother of pearl - half brother of pearls

It just didn't come out in shape. If a pearl is a spherical formation (or close to a sphere in shape), then it is only deposited on the walls of the shell.

The demand for mother-of-pearl has always exceeded the demand for pearls due to the low price and wide availability of the material. Pearls are rare, and there are tons of mother-of-pearl in any river. Mollusk shells, covered with a thick layer of mother-of-pearl, have been used to make buttons, combs, handles and other consumer goods for many centuries. Today there is no type of plastic that would be used as widely and actively as mother-of-pearl in the recent past.

Once palm trees grew everywhere

...because it was warm and humid. The petrified palm stem can be found in coal deposits, in shale, and in quartz deposits. It is silicates that make palm wood an aesthetically expressive stone.

It should be noted that in its botanical essence, the palm tree is a tree-like, but herbaceous plant. You can't find annual rings on palm trees! On the other hand, the longitudinal vessels, through which the nutrient juices circulated throughout the plant, are very clearly visible. They - both on the transverse and on the longitudinal cut of petrified palm wood - make up the beauty of the stone.

The soft starchy core of the palm trunk is not rich in vessels, and therefore is replaced during fossilization by a homogeneous siliceous material.

Various silicas, impregnating the trunks of flooded, covered, drowned trees in swamps, often turn unremarkable wood into a precious gem. Silicates, colored with a variety of mineral impurities, acquire an iridescent color. A chip, saw cut, and even better, a thin section often amazes with the richness of the natural palette of colors.

In this case, the layered wood structure remains, as a rule, well distinguishable. That just adds to the decor. beautiful stone biological origin.

Stromatolite jaspers

Jasper Rock Mary Ellen is located in the state of Minnesota (USA). It is famous for the fact that the main masses of the rocks that make up the mountain - red jasper and silver hematite - are intertwined in unimaginable clubs and twists.

Red and black is an advantageous color combination for any artistic subject. However, stromatolites, formed from layered colonies of cyanobacteria two billion years ago, rarely turn red. Only on the American continent were found traces of the first steps of life on the planet, made by red jasper on black iron ore...

petrified corals

A polished petrified one makes you want to blow off dust particles from it - the jewelry work of nature is so fine. Cellular frameworks of marine organisms of the distant past are delicately arranged and skillfully "executed". The resemblance of fossil coral to the work of a skilled craftsman is endless!

Quartz and calcite, replacing organic tissue in fossilized corals, make jewelry durable. However bright colors, characteristic of modern corals, fossil polyps do not have. Fiery red or transparent yellow earrings made of petrified corals are the product of handicraft "improvement".

"Sand Dollar"

"Sand dollar" in both Americas is called the skeleton sea ​​urchin, classified as incorrect (such is zoological terminology). Correct hedgehogs- round echinoderms, irregular - flat. They have been living on Earth for a long time, and in some places they inhabit the shelf bottom so densely that they lie on the sand like scales on the body of a crucian carp - or even in two layers.

Wrong hedgehogs they have a very conditional needle protection, and therefore everyone who is not lazy feeds on them. Nevertheless, many of the flat as a toy saucer animals manage to grow a decent thickness of the skeleton, live to a natural death and please people with the sight of their skeleton - the "sand dollar". Especially highly valued are dollars "issued" millions of years ago...

Ammonites

Anyone who has been interested in the history of evolution knows about the ammonites. They - sometimes quite modest in size, sometimes under two meters in diameter - are twisted into a flat spiral, like the horns of the god Amun in one of his earthly incarnations. Ammonites are easy to find in natural screes. In some European countries, they have long been called "golden snails".

Ammonite "gold" is a layer of petrified mother-of-pearl in sealed shell chambers. The most beautiful ammonites are mined in the Canadian province of Alberta. The iridescent radiance of the polished walls of the shells surpasses the play of color in opal and labradorite.

dinosaur bone

The process of bone petrification is extremely lengthy, because each molecule of calcium phosphate (of which, in fact, bones are composed) must be replaced by a molecule of silicon dioxide. It takes at least two million years for a medium-sized dinosaur skeleton to turn into a precious gem!

Fortunately, something, but dinosaur bones have enough time with a large margin. For 65 million years separating us from the last animal lizards of the Earth, many tons of bones turned into colored quartz. Moreover, a considerable part of quartz took on impurities, which allowed the hitherto unattractive natural material to acquire both the look, the pattern, and the texture at a good jewelry level. Dinosaur bone cabochons are often extremely attractive!

Ivory is younger than dinosaur bones. Today, under the name "ivory", African and Indian elephant, fossil mammoths, walrus tusks, teeth of hippopotamus and sperm whale.

The main thing is its luxurious appearance. However, the manufacturability of the material is also important. Last but not least, artisans fell in love with ivory because of its ability to become plastic, and then harden again.

Ivory color varies. The white and blue tooth of the hippopotamus is valued, warm shades(up to red-brown) mammoth tusk, translucent whiteness of the tusk of a young elephant.

The list of stones of biological origin can go on and on. The gallery of precious gems is replenished by the efforts of geologists, researchers, pioneers of remote areas of the planet.

Like the glow of dawn

The first pearls people found in search of food. Oysters producing this gem are still loved by gourmets. For thousands of years, people have been admiring the radiance of pearls that have grown by the will of nature - and for several decades now we have been forcing mollusks to envelop seed grains of sand in multi-colored layers.

Today's pearls are all colors of the rainbow and even the colors of the night! But, as in the old days, this is a stone in which at least half of the mass falls on organic tissue. We looked at pearls in more detail in the article, and you can be sure that this stone of biological origin has been in favor with fashionistas for a reason for the fifth millennium in a row!

Frozen sunshine...

... poetically called amber. Both honey-transparent and the most “foggy” forms of the stone really give the impression of clots of luminous substance. There are countless varieties of amber! The color range of this natural jewel ranges from milky white through all shades of yellow and red to blue and green. There are amber and black!

Every amber is a piece of fossilized resin of a tree that grew millions of years ago. There are ambers born in pine groves, and ambers derived from resin tropical trees. We talked about amber in the articles: and. Now the time has come to pay attention to the trees that grew hundreds of millions of years ago, and by our time have turned into "precious stones".

"Peanut" wood

Wood with a clear structuring of the array during fossilization can also give an unexpected visual effect. Particularly interesting are the fossilized wood remains that have spent many years under water. The point, in fact, is not in the water, but in the mollusks that inhabit the reservoirs of the planet. Some of them feed on rotting wood, and in the process of obtaining food they go deep into the flooded logs, gnawing through numerous passages.

The subsequent mineralization of organics led to a striking result. The cavities gnawed (more precisely, machined) by the mealybug were filled with white quartz. The fabrics of the tree remained colored. Minerologists dubbed this kind of petrified wood "peanut forest" - for the similarity of the stone pattern with sprouting peanuts is almost one hundred percent.

Jet

However, not all plant remains of the distant past are so lucky. Jet, a mineral related to coal, is recognized as the same prehistoric wood that survived flooding in the silt layers two hundred million years ago.

Unattractive in its raw form, polished jet shines like silk velvet. The best varieties stones are distinguished by a mirror gloss and are used to make jewelry. In the recent past, a lot of haberdashery trifles were made from jet - like buttons, beads, beads. served its owners no worse than mother-of-pearl.

corals

Most of the bottom marine sediments are formed by calcareous remains of organisms that lived in time immemorial. However, corals, having won a warm place five hundred million years ago, thrive to this day.

Calcareous skeletons of corals have three and a half hundred variants of natural coloration. Polished coral is an excellent material for making jewelry. However, the user must remember: the thicker the color of the coral, the more organic matter, and the more carefully you need to treat the subject.

Modern views corals are different from the polyps that inhabited the earth's seas in past geological epochs. However, we can say with confidence: petrified corals are extremely beautiful and interesting!

Compressed carcasses of sea lilies

sea ​​lilies crinoids once so abundantly inhabited the shallow bottom warm seas that their calcareous cores - mostly tubular, divided into short segments - became a rock-forming element. Many of the most interesting specimens of these Proterozoic pufferfish were obtained during the construction of the Moscow Metro.

However, crinoid limestone, formed by the remains of flower-like animals three hundred million years ago, under (in literally) Moscow does not meet. Although this mineral is widely distributed.

Distinguishable remains of crinoids, “soldered” into the thickness of a translucent mineral, are sometimes very decorative. Such stones become a worthy decoration.

Under the sonorous name hides the most beautiful mineral with unusual story. Actually, turritella terebra is the name sea ​​mollusk with a helical shell. They say that it was turitella shells that prompted the legendary Archimedes to construct a water-lifting propeller.

Turitella agate is, in fact, a scattering of shells of a mollusk of this species, which are in varying degrees of preservation, filled with hardened silicate. Many of the real turitell agates include sand, water, air bubbles.

Take a closer look at appearance precious stone! Under the name of agate-turitella, any petrified garbage is often sold. If you do not see distinctly preserved elements of cone-spiral shells, this is a fake!

A large group of rocks occurs in various water bodies and in places on
drier as a result of various chemical processes and vital activity of animals and plants, as well as due to the accumulation of organic residues after the death of animals and plants. Among them, carbonate rocks, siliceous, sulphate and halide, ferruginous, phosphorite and caustobiolites can be distinguished.

The group of carbonate rocks includes limestone, dolomite and marl.

Limestones(CaCO 3) are the most widespread and are formed both by chemical precipitation and mainly by organogenic. Organogenic limestones are usually composed of calcareous shells of mollusks, remains of crinoids, calcareous algae, corals, etc. Depending on the predominance of the remains of certain marine organisms, limestones are called coral, brachiopod, foraminiferal, etc. Among limestones of chemical origin, the following are known: oolitic limestones, which are accumulation of spherical calcareous grains-oolites; calcareous tufas deposited by springs rich in bicarbonate of lime dissolved in water.

writing chalk is a rock formed in two ways. A significant part of it, about 60-70%, is the remains of skeletal formations of planktonic organisms, the rest - fine-grained, powdery calcite - arose chemically.

Marl gives another example of a rock, which has arisen in two ways. It consists of 50-70% CaCO 3 of organic origin, and the remaining 50-30% falls on clay particles, which include particles of both detrital and chemical origin.

Dolomites in terms of chemical composition, they are (by 90-95%) a double carbonate salt of calcium and magnesium CaMg(CO 3) 2 . With a content of at least 50% CaCO 3, the rock is called calcareous dolomite. They can be formed by precipitation from water with high salinity, in which case dolomite layers often alternate with gypsum layers. But more often, dolomites are formed as a result of alteration ("dolomitization") by the corresponding solutions of limestones (or lime sediments before the transformation of the latter into rock) - the so-called exogenous-metasomatic replacement of limestones, as well as by the hydrothermal-metasomatic way (at low temperature).

Siliceous rocks

diatomaceous earth- loose, earthy or weakly cemented yellowish or light gray rock, consisting of an accumulation of skeletal remains composed of hydrous silica (opal) and belonging to microscopic diatoms. They sometimes contain a small admixture of clay particles, grains of quartz and glauconite.

Tripoli similar in properties to diatomite, but differs from it in the absence of remains of obvious organic origin. The rock is composed of the smallest opal grains.

Flask- siliceous light rock, consisting of opal silica (up to 90%) with a small admixture of remains of radiolarians and diatom shells, with grains of quartz, glauconite and clay particles. Most often, the flasks are hard, the fracture is conchoidal, the color is from bluish-gray to almost black.

flint concretions(concretions) are widespread among sedimentary rocks. They are formed different ways. Some of them arise from the solutions circulating in the rocks by filling the voids in the rocks with the opal-chalcedony substance. Others are formed in the process of diagenesis (regeneration of sediment into rock) by growing around a center from foreign matter as a result of the action of crystallization forces. Concretions with voids inside are called geodes, with hard core inside - nodules. Siliceous concretions are found in many rocks, but they are especially frequent in limestone strata.

Sulfate and halide rocks, despite the diversity of their chemical composition, are united by the commonality of their origin. Their homeland is drying lagoons and salt lakes separated from sea water bodies. This group of rocks includes such single-mineral rocks as anhydrite (CaSO 4), gypsum (CaSO 4 2H 2 O), rock salt(NaCl).

Iron rocks. Most widespread and practical value among them are oolitic brown iron ore, consisting of small, rounded, concentrically shelled or radially radiant formations.

Phosphorite rocks are sedimentary rocks containing 12-40% P 2 O 5 . According to the form of occurrence, phosphorites are distinguished as concretional or nodular, when they are represented by nodules of spherical or irregularly rounded shape, and reservoir, when they are cemented into conglomerate slabs.

Caustobioliths(organogenic combustible rocks). Among them stand out caustobiolites of the coal series, which include peat, brown coal, hard coal, anthracite and caustobiolites of the bitumen series - oil.

Peat consists of semi-decomposed plant remains accumulated over a long period in the specific conditions of swamps and lakes. Decomposition occurred in water with the participation of various microorganisms and with insufficient air flow. The total thickness of peat can sometimes reach several meters. Peat organic matter contains carbon (from 28 to 35%), oxygen (30-38%), hydrogen (5.5%).

brown coals are also a product of changes in plant sediments of former geological periods. Brown coals are harder and denser than peat: specific gravity is 1.1-1.3. They contain an admixture of clay material, which causes their high ash content. The carbon content in them is in the range of 67-78%. They are a transitional rock from peat to coal.

hard coals represent the next stage in the change of brown coals. They are black, dense, have a greasy or resinous sheen and form a black line on the porcelain plate. Specific gravity - 1.0-1.8; hardness - 0.5-2.5. The carbon content reaches 80-85%.

Anthracite - the last stage of the process of metamorphosis of solid plant remains. The specific gravity of anthracites is 1.3-1.7; hardness - 2.0-2.5; black colour; gloss - semi-metallic; line is black. The carbon content is 95-97%.

Oil- natural combustible oily liquid Brown. The composition of oil includes C, O, H, of which the main role belongs to carbon and hydrogen. Oil is a mixture of liquid hydrocarbons of methane (C n H 2 n +2), naphthenic (C n H 2 n) and aromatic (C n H 2 n -6) series. The specific gravity of oil is 0.8-0.9. Oil is formed in the thickness of the accumulated at the bottom water basins sedimentary rocks in the presence of dispersed organic matter among silt particles, which is converted into oil with the participation of organic and inorganic catalysts, under conditions of a strictly reducing environment.

Chemical sedimentary rocks are formed by precipitation from aqueous solutions of chemical precipitation. These rocks include: various limestones, calcareous tuff, dolomite, anhydrite, gypsum, rock salt, etc. A common feature is their solubility in water and fracturing.

Organogenic sedimentary rocks formed as a result of the accumulation and transformation of the remains of the animal world and plants, are characterized by significant porosity, dissolve in water. Organogenic rocks include: shell limestone, diatomite, etc.

The vast majority of the breeds of these two groups are of mixed (biochemical) origin.

Groups of chemical and organogenic rocks are usually divided into subgroups according to composition:

carbonate,

siliceous,

glandular,

halogen,

sulfate,

phosphate and etc.

Combustible rocks stand out, or caustobioliths.

Carbonate rocks

Limestone - a rock composed of the mineral calcite. It is determined by a vigorous reaction with HCl. Color white, yellowish, gray, black. Limestones are of organogenic and chemical origin.

Organogenic limestones consist of the remains of organisms, which are rarely preserved completely, more often they are crushed and also changed by subsequent processes. If the limestone consists of whole shells, it is called shell limestone, and if it is made of broken shells, it is called detritus limestone.

A variety of organogenic limestone is a piece of chalk, consisting mainly of the smallest shells of foraminifers, powdery calcite and shells of the simplest microscopic algae. Chalk- white earthy rock, widely used as a raw material for Portland cement, whitewashing material and writing chalk.

Limestones of chemical origin occur in the form of dense fine-grained masses:

oolitic limestones- accumulations of small balls of a shellish or radial-radiant structure, connected by lime cement;

calcareous tuff(travertine) - a highly porous rock formed in places where rich dissolved lime bicarbonate comes to the earth's surface groundwater, from which, when carbon dioxide volatilizes or when water cools, an excess of dissolved calcium carbonate quickly precipitates;

Sinter formations of calcite- stalactites, stalagmites (Fig. 9).

Limestones are used as a building material, fertilizer, in the cement industry, in metallurgy (as a flux).

Dolomite CaMg(CO 3) 2 – consists of a mineral of the same name. Outwardly similar to limestone, differs from it in the reaction with hydrochloric acid (reacts in powder), yellowish-white, sometimes brownish color, greater hardness (3.4–4). Dolomites are formed in marine basins mainly as secondary products due to limestones: magnesium dissolved in water interacts and combines with limestone calcite. This process, called dolomitization, leads to the complete destruction of organic residues. Thin layering is not typical for dolomites; they often form powerful rocky cliffs. Dolomites are used as a flux, refractory and fertilizer.

Marl - calcareous-argillaceous rock, consisting of calcite and clay particles (30–50%). Its color is pale-yellow, brownish-yellow, white, gray. Outwardly, marl is little different from limestone; it is recognized by the nature of the reaction with hydrochloric acid, from a drop of which a dirty-damp or whitened spot remains on the surface of the marl, due to the concentration of clay particles at the reaction site. Marl is formed in the seas and lakes (Fig. 10).

kpeominous rocks

They can be both chemical (siliceous tuff) and organogenic origin (flint, diatomite, flask).

Siliceous tuff (geyserite) consists of a porous (rarely dense) mass of opal. The color of the breed is light, sometimes variegated. Tuff is formed when hot springs come to the surface, in the water of which silica is dissolved.

Flint- a fine-grained spotted or banded aggregate of chalcedony, a cryptocrystalline variety of quartz. It is formed from the decayed skeletal remains of siliceous organisms, that is, from silica gel, which, gradually losing water and compacting, turns into opal and then into chalcedony. Often contains inclusions of organic residues. The color is predominantly gray to black or brown, occurs as nodules (nodules) in Cretaceous limestones, never forming coherent layers. In the Stone Age, due to its high hardness (equal to 7), flint served as an important material for the manufacture of weapons and tools. It is currently used as a grinding and polishing material.

diatomaceous earth - porous, light, white, light yellow loose or cemented rock, easily pounded into a fine powder, greedily absorbs water. It consists of the smallest opal shells of diatoms, skeletons of radiolarians and sponge needles, grains of quartz, glauconite, and clay minerals are found. It is used as a filter material and to obtain liquid glass. Diatomite is formed from diatomaceous silt located at the bottom of lakes and seas.

Flask – siliceous, porous rock of white, gray, black color, often with conchoidal fracture. The hardest varieties of it, when struck, break with a characteristic ringing sound. It consists of opal grains and an insignificant admixture of remains of siliceous skeletons of organisms cemented with siliceous matter.

ferruginous rocks

Among the rocks of this subgroup, siderite (FeCO 3 - iron spar) and limonite are the most common.

Limonite- a mechanical mixture of iron hydroxide with sandy or clay material. In appearance, these are most often legume (oolitic) or sinter masses. The color is yellow, brown, accumulates in swamps and lakes, therefore it is often called swamp or lake ore.

halide rocks

From halide rocks most common rock salt, mineral halite(NaCl), in nature it is usually colored gray, reddish-yellowish or reddish. Rock salt usually occurs in layers, has a coarse grained structure and glistens in the sun. A third of all salt produced is used as food for people and animals, the rest is used in industry for technical purposes. In the deposit, layers of rock salt often alternate with layers sylvina(KCl).

Sulfuric rocks

The most widespread gypsum and anhydrite. They are formed as a result of precipitation from aqueous solutions in shallow lakes, lagoons of arid zones, where, due to intense evaporation, supersaturated solutions arise.

Halide and sulfate salts usually occur in the form of layers among clayey rocks; the latter protect them from dissolution by groundwater.

Gypsum(CaSO 4 ∙ 2H 2 O) – white or lightly tinted; coarse-grained or fibrous, with a silky sheen. It differs from a similar anhydrite having a hardness of 3–4 by a lower hardness of 1.5–2. Widely used in construction. By firing gypsum, 75% of crystallization water is removed from it, but if water is added to the fired building gypsum, it quickly absorbs it again, restoring its original water content, which is accompanied by an increase in volume. This is the basis for the technical use of gypsum as a cement and binder.

Anhydrite(CaSO 4) - this is the name of both the salt rock itself and the mineral that composes it, it looks like rock salt, whitish-gray, yellowish, bluish in color, but has a fine-grained structure and does not possess salty taste. It is used in the production of mineral fertilizers and in construction. Anhydrite layers are dangerous in tunnel construction, as they swell extremely strongly when water enters and, as a result, can compress the tunnel walls.

Phosphate rocks

These include many sedimentary rocks enriched in calcium salts of phosphoric acid with a P 2 O 5 content of up to 12–40% or more. calcium phosphates are more common apatite.

As part of phosphorites admixtures of quartz, calcite, glauconite, remains of radiolarians, diatoms and other organic substances are observed. Phosphate rocks occur in the form of nodules and beds. They are formed both chemogenic and biogenic in the seas and on the continents (in lakes, swamps, caves). In the seas, phosphorites appear when chemical precipitation occurs at depths of 50 to 150 m. . The color of phosphorites is gray, dark gray, black. They are used as raw materials for fertilizer (superphosphate) and phosphorus production.

Caustobioliths

This is a large group of combustible carbonaceous rocks of organic composition and organogenic origin, and therefore, according to a strict definition, they are not real rocks. But, on the other hand, they are an integral part of a solid earth's crust and are partially altered to such an extent that their organic nature can no longer be established, and therefore they are classified as sedimentary rocks.

Caustobioliths are formed by coalification of accumulations of plant material. The carbonification process consists in a gradual increase in the relative content of carbon in organic matter due to its depletion in oxygen (and to a lesser extent in hydrogen). Increased pressures and temperatures associated with mountain-forming and volcanic processes cause diagenetic and metamorphic transformations of coals.

Caustobiolites are solid (peat, brown coal, coal, anthracite, graphite, oil shale, asphalt, ozocerite), liquid (oil) and gaseous (combustible gases). The properties of solid caustobiolites are given in Table. eight.

Table 8

Properties of solid caustobiolites

Caustobioliths			Density, g / cm 3	Calorific value ability
		(no shine)		1500-2000 cal (6280–8374 J)
Brown coal	brownish black			2000–7000 cal (8374–29 308 J)
Coal				7000-8500 cal (29308–35588 J)
Anthracite		metalloid		8500-9000 cal (35588–37681 J)
		Metal

Peat consists of semi-decomposed marsh and woody plant remains containing carbon (35–59%), hydrogen (6%), oxygen (33%), nitrogen (2.3%) in its composition. Peat is a loose, brownish-brown or black rock. Depending on what plant residues peat consists of, there are sphagnum, sedge and reed peat. Raw peat contains up to 85–90% water; when dried to an air-dry state, it still contains up to 25% water. Peat is used for the preparation of fertilizers and technical wax.

Brown coal contains 67–78% carbon, 5% hydrogen and 17–26% oxygen. This is a dense dark brown or black mass with an earthy fracture, a matte sheen, a dark brown streak. Hardness 1–1.5; density 1.2 g/cm 3 . Brown coals contain impurities of clay minerals, which cause their high ash content.

Coal contains up to 82–85% carbon. The breed is black, dense, matte luster, black streak. Hardness from 0.5 to 2.5; density 1.1–1.8 g / cm 3.

Anthracite contains 92–97% carbon. It is a hard brittle grayish-black rock with a strong semi-metallic luster. The fracture is granular, conchoidal. Hardness 2.0–2.5; anthracite density 1.3–1.7 g / cm 3. The line color is light black. Formed at high pressure and temperature (not lower than 300 °C).

Graphite– crystalline carbon; this is a highly metamorphosed coal, but it can also be of inorganic origin.

oil shale - shale, clay or marl rocks, which include organic matter in the form of dispersed sapropel (putrefactive silt). Oil shales are thin-layered, have a dark gray or brown color; they were formed in the process of accumulation of dead microalgae and plankton. They are used as local fuel and for the production of liquid and gaseous volatile substances, from which oil products, gas, sulfur, drying oil, tanning extracts, paints, pesticides for plant protection are obtained.

Oil is a mixture of liquid and gaseous hydrocarbons. The share of other elements (nitrogen, oxygen, sulfur, etc.) accounts for 1–2%. In appearance it is an oily liquid, the color varies from almost white, yellow to dark brown; the density also changes accordingly - from 0.76 to 1.0 g / cm 3. Only asphalt oils have a slightly higher density.

Amber (C 10 H 16 O) - hardened resin of coniferous trees that grew 25-30 million years ago. Amber is amorphous. Its color is white, yellow, brownish. Hardness 2–2.5. Transparent or translucent. The gloss is oily or matte. Density 1.05–1.1 g / cm 3, melts at a temperature of 300 ° C. It burns with a pleasant smell. When rubbed, it is easily electrified. It occurs in the form of blocks among sandy rocks. It is used in the jewelry industry and in certain medical preparations.

The main sedimentary rocks of organic and chemical origin are given in Table. nine.

Table 9

Main rocks of organic and chemical origin

Name subgroups	Organogenic rocks	Chemogenic rocks
Carbonate	coral limestone, shell limestone, detritus limestone, chalk, marl	dense limestone, oolitic limestone, calcareous tuff, sinter limestone, dolomite, siderite, marl
Siliceous	diatomite, flask	tripoli, siliceous tuffs, flint
glandular
Halogen		rock salt
sulfate		gypsum, anhydrite
Aluminum
Phosphate		phosphorites
Caustobioliths	peat, fossil coals, oil shale, oil, asphalt, ozocerite, amber