For many peoples, gypsum was the breadwinner. But even entire cities were built of gypsum! Blocks sawn from crystalline gypsum were used to build the walls of the city of Risafa (Syria). White stone shines dazzlingly in the hot sun even today, when only picturesque ruins remain of the city...
Sculptors all over the world could not work if the world did not have a light, inexpensive and easy-to-use material called gypsum. Gypsum is appreciated by traumatologists, painters, plasterers, and paper manufacturers.
Physical properties of gypsum
The crystals are thick and thin tabular, sometimes very large. The aggregates are dense, granular, foliated, fibrous (selenite). The color of the crystal is white, often transparent, sometimes gray and pink from impurities. The line is white. The luster is glassy, in fibrous varieties of gypsum it is silky. Hardness 2 on the Mohs scale. Density 2.3 g/cm3.The chemical formula is Ca(SO4)2H2O.
Origin and deposits
The origin of gypsum is different. In some deposits, a mineral is concentrated that has accumulated as marine sediment, chemically altered during the drying of brine lakes. Elsewhere, gypsum formed as a result of the weathering of compounds and sediments. native sulfur- in this case, mineral deposits are often contaminated with clays and rock fragments.Gypsum deposits are found on all continents. Large Russian developments conducted in the Urals and the Caucasus. Gypsum is mined mountainous areas Asia and America (the USA is the champion of gypsum production), in the foothills of the Alps.
Medicinal properties of gypsum
official medicine makes extensive use of the astringent properties of gypsum. The hygroscopicity of the material allows it to be used as effective remedy from sweating. Gypsum-oil emulsion is used in medical cosmetology as a substance that restores skin turgor.Not so long ago, science found out: the crystalline structure of gypsum, as if on purpose, was created to hold heavy metal ions. Lithotherapists responded to the discovery: today, wet wrapping in crushed gypsum is becoming more common. Calcium and sulfur literally pull harmful substances out of the skin and thus gradually heal the body.
Examining a selenite (selenite is a fibrous variety of crystalline gypsum) ball helps to calm down nervous system while concentrating.
The magical properties of gypsum
The main magical property of gypsum is the ability to absorb passions. That is why the possession of plaster decorations is recommended for people who are nervous, quick-tempered, hot. Aries and Capricorns, Lions and Sagittarius can successfully use plaster talismans to optimize their own behavior.It is difficult to use gypsum crystals in magical rituals: a stone can show a person the vanity of his undertakings, the wretchedness of his goals, and the primitiveness of his actions. The magically destructive role of gypsum is useful for convinced proud and self-confident half-educated people, but it can do a disservice to a person who is not too self-confident.
The use of plaster decorations
Beyond purely practical use, gypsum can be used as an excellent interior decoration. Speech in this case it is not about gypsum stucco, a frequent architectural element of the premises, but about crystalline formations."Desert roses" - this is the name of the intergrowths of smoothly curved gypsum plates, really resembling flowers. The similarity is especially strong if the size of the natural aggregate does not exceed the size of a garden rose flower, the color of the plates is white to translucent, and the "petals" themselves are thin, like real petals.
Such specimens are relatively rare and therefore expensive. More often, “desert roses” are nondescript, harvested by hundreds of local collectors, sold by weight ... Nevertheless, even the most modest cream-colored plaster “rose” can become an interior object of admiration and a source of positive aesthetic impressions.
Gypsum crystals in nature can grow to gigantic sizes and at the same time differ in an enviable optical quality. However, gypsum rarely gets cut: the crystalline druze of the mineral is very diverse and very decorative. A collection of gypsum crystals can be collected for a lifetime, but display all forms natural diversity unlikely to succeed!
Gypsum in art
Colorless lamellar crystals of gypsum in Russian language tradition are called "marina glass". The name comes from the past. In the old days, such plaster (especially specimens with a mother-of-pearl tint) was used to frame images. Especially often, transparent or iridescent cast gypsum was used to decorate the icons of the Virgin Mary. Hence the "marino glass".Fibrous gypsum, found in the Urals in the century before last, immediately became an object of adoration among lovers of elegant knick-knacks. Mineral, as if luminous inner light, received the sonorous name "selenite" and became the main material for the manufacture of figurines. Some varieties of selenite, having the effect of asterism, allow you to carve mystically shimmering sculptural miniatures.
Jewelry made of crystalline gypsum is more of a souvenir character. The fragility of the stone, which is extremely subject to abrasive wear, does not allow cabochons and rings carved from a gypsum monolith to retain their attractiveness for a long time.
Dehydrated gypsum, called anhydrite, resembles marble in appearance and properties. For two centuries, the once popular cabinet writing instruments were also cut from anhydrite. Today, this mineral is used to make sculptural interior decorations.
However, those buyers of anhydrite figurines who place their purchases in greenhouses, winter gardens, swimming pools and other wet rooms are mistaken. In the presence of water, anhydrite absorbs moisture, gradually (not necessarily proportionally) increases in size and loses its decorative effect.
Gypsum- mineral, aqueous calcium sulfate. The fibrous variety of gypsum is called selenite, and the granular variety is called alabaster. One of the most common minerals; the term is also used to refer to the rocks he composed. Gypsum is also commonly called a building material obtained by partial dehydration and grinding of the mineral. The name comes from the Greek. gypsos, which in ancient times meant both gypsum itself and chalk. A dense, snow-white, cream, or pink, fine-grained variety of gypsum is known as alabaster.
See also:
STRUCTURE
The chemical composition is Ca × 2H 2 O. The syngony is monoclinic. The crystal structure is layered; two sheets of 2- anionic groups closely associated with Ca 2+ ions form double layers oriented along the (010) plane. Molecules of H 2 O occupy places between these double layers. This easily explains the very perfect cleavage characteristic of gypsum. Each calcium ion is surrounded by six oxygen ions belonging to the SO 4 groups and two water molecules. Each water molecule binds a Ca ion to one oxygen ion in the same double layer and to another oxygen ion in the adjacent layer. PROPERTIES
The color is very different, but usually white, gray, yellow, pink, etc. Pure transparent crystals are colorless. Impurities can be colored in various colors. The dash color is white. The luster of the crystals is glassy, sometimes with a mother-of-pearl tint due to microcracks of perfect cleavage; selenite is silky. Hardness 2 (standard on the Mohs scale). Cleavage is very perfect in one direction. Thin crystals and cleavage plates are flexible. Density 2.31 - 2.33 g / cm 3.
It has significant solubility in water. A remarkable feature of gypsum is the fact that its solubility reaches a maximum at 37-38°C with increasing temperature, and then drops rather quickly. The greatest decrease in solubility is established at temperatures above 107 ° due to the formation of a "hemihydrate" - CaSO 4 × 1 / 2H 2 O.
At 107°C, it partially loses water, turning into White powder alabaster, (2CaSO 4 × H 2 O), which is noticeably soluble in water. Due to the smaller number of hydrate molecules, alabaster does not shrink during polymerization (increases in volume by approx. 1%). Under p. tr. loses water, splits and fuses into white enamel. On charcoal in a reducing flame it gives CaS. It dissolves much better in water acidified with H 2 SO 4 than in pure water. However, at a concentration of H 2 SO 4 over 75 g/l. solubility drops sharply. Very slightly soluble in HCl.
MORPHOLOGY
Due to the predominant development of (010) faces, crystals have a tabular, rarely columnar, or prismatic appearance. Of the prisms, (110) and (111) are the most common, sometimes (120) and others. Faces (110) and (010) often have vertical shading. Intergrowth twins are frequent and are of two types: 1) Gallic according to (100) and 2) Parisian according to (101). It is not always easy to tell them apart. Both of them resemble a dovetail. Gallic twins are characterized by the fact that the edges of the prism m (110) are parallel to the twin plane, and the edges of the prism l (111) form a reentrant angle, while in the Parisian twins the edges of the prism Ι (111) are parallel to the twin seam. It occurs in the form of colorless or white crystals and their intergrowths, sometimes colored by inclusions and impurities captured by them during growth in brown, blue, yellow or red tones. Intergrowths in the form of a “rose” and twins are characteristic - the so-called. "dovetails"). It forms veinlets of a parallel fibrous structure (selenite) in clayey sedimentary rocks, as well as dense continuous fine-grained aggregates resembling marble (alabaster). Sometimes in the form of earthy aggregates and cryptocrystalline masses. It also forms the cement of sandstones.
Common are pseudomorphs after gypsum of calcite, aragonite, malachite, quartz, etc., as well as pseudomorphs of gypsum after other minerals.
ORIGIN
A widely distributed mineral natural conditions formed different ways. Sedimentary origin (typical marine chemogenic sediment), low-temperature hydrothermal, found in karst caves and solfataras. Precipitated from sulphate-rich aqueous solutions during the drying of sea lagoons, salt lakes. Forms layers, layers and lenses among sedimentary rocks, often in association with anhydrite, halite, celestite, native sulfur, sometimes with bitumen and oil. In significant masses, it is deposited by sedimentation in lacustrine and marine salt-bearing dying basins. At the same time, gypsum, along with NaCl, can be released only in initial stages evaporation when the concentration of other dissolved salts is not yet high. Upon reaching a certain value of the concentration of salts, in particular NaCl and especially MgCl 2, anhydrite will crystallize instead of gypsum and then others, more soluble salts, i.e. the gypsum in these basins must belong to the earlier chemical sediments. Indeed, in many salt deposits, layers of gypsum (as well as anhydrite), interbedded with layers of rock salt, are located in lower parts deposits and in some cases are underlain only by chemically precipitated limestones.
In Russia, thick gypsum-bearing strata of Permian age are distributed in the Western Urals, in Bashkiria and Tatarstan, in Arkhangelsk, Vologda, Gorky and other regions. Numerous deposits of the Upper Jurassic age are established in the North. Caucasus, Dagestan. Remarkable collection specimens with gypsum crystals are known from the Gaurdak deposit (Turkmenistan) and other deposits. Central Asia(in Tajikistan and Uzbekistan), in the Middle Volga region, in Jurassic clays Kaluga region. In the thermal caves of Naica Mine, (Mexico), druze of gypsum crystals of unique size up to 11 m long were found.
APPLICATION
Today, the mineral "gypsum" is the main raw material for the production of α-gypsum and β-gypsum. β-gypsum (CaSO 4 0.5H 2 O) is a powdered binder material obtained by heat treatment of natural two-water gypsum CaSO 4 2H 2 O at a temperature of 150-180 degrees in apparatus communicating with the atmosphere. The product of grinding β-modification gypsum into a fine powder is called building gypsum or alabaster, with finer grinding, molding gypsum is obtained or, when raw materials of increased purity are used, medical gypsum. During low-temperature (95-100 °C) heat treatment in hermetically sealed apparatus, α-modification gypsum is formed, the grinding product of which is called high-strength gypsum.
In a mixture with water, α and β-gypsum hardens, turning back into dihydrate gypsum, with heat release and a slight increase in volume (approximately 1%), however, such a secondary gypsum stone already has a uniform fine-crystalline structure, the color of various shades of white (depending on raw materials), opaque and microporous. These properties of gypsum are used in various fields human activities.
Gypsum (English Gypsum) - CaSO 4 * 2H 2 O
CLASSIFICATION
| Strunz (8th Edition) | 6/C.22-20 |
| Nickel-Strunz (10th edition) | 7.CD.40 |
| Dana (7th edition) | 29.6.3.1 |
| Dana (8th edition) | 29.6.3.1 |
| Hey's CIM Ref. | 25.4.3 |
PHYSICAL PROPERTIES
| Mineral color | colorless turning into white, often colored by minerals-impurities in yellow, pink, red, brown, etc.; sometimes there is a sectorial-zonal color or distribution of inclusions over growth zones inside the crystals; colorless in internal reflexes and through. |
| Dash color | white |
| Transparency | transparent, translucent, opaque |
| Shine | glassy, close to glassy, silky, pearlescent, dull |
| Cleavage | very perfect, easily obtained from (010), almost mica-like in some samples; according to (100) clear, turning into conchoidal fracture; by (011), gives a splintery fracture (001) |
| Hardness (Mohs scale) | 2 |
| kink | smooth, conchoidal |
| Strength | flexible |
| Density (measured) | 2.312 - 2.322 g / cm 3 |
| Radioactivity (GRapi) | 0 |
Gypsum- a natural mineral from the class of sulfates. Of all natural sulfates in the construction industry, highest value. In nature, it is in the form of a dihydrate - dihydrate calcium sulfate CaSO 4. 2H 2 O and in an anhydrous state - anhydrite CaSO4.
Basically, gypsum is used mainly as a raw material for the production of low- and high-firing gypsum binders and as an additive introduced when grinding Portland cement clinker and its varieties in order to control the setting time.
Another direction of using natural gypsum is the manufacture of wall and partition products, which is due to its low thermal conductivity: at 30 ° C 0.28-0.34 W / (m.K).
Natural gypsum dihydrate is a rock of sedimentary origin, composed mainly of large and small CaSO 4 crystals. 2H 2 O. Intergrowths of gypsum crystals can form plaster roses. Dense formations of gypsum are called gypsum stone.
Structural differences
By appearance and the structure of the rock are distinguished:
- crystal transparent plaster;
- poikilitic or sandy gypsum - crystals overflowing with sand.
Poikilit(eng. Poikilite) - a crystal or grain that contains numerous inclusions of other minerals that were captured during the growth of the individual.
- gypsum spar- a lamellar mineral with flat transparent crystals of a layered structure, individuals are quite large sizes, transparent (Marin's eye);
- selenite- parallel-fibrous gypsum, yellowish color with a silky sheen
- granular gypsum;
- alabaster
There are crystalline, fibrous, granular and sandy varieties of gypsum.
Under difference imply a set of mineral individuals of the same mineral species, differing in morphological features. For example, the differences of gypsum: "Maryino glass" - lamellar gypsum, selenite - fibrous gypsum.
Gypsum forms continuous marble-like masses, veined accumulations, as well as single crystals and druses. The appearance of its crystals is usually lamellar, columnar and acicular.
Physical properties of gypsum
Crystal lattice of dihydrate gypsum and anhydrite
AT crystal lattice in gypsum dihydrate, each calcium atom is surrounded by six complex groups, consisting of four tetrahedra and two water molecules. The structure of the crystal lattice of this compound is layered. The layers are formed, on the one hand, by Ca 2 + ions and SO 4 -2 groups, and on the other hand, by water molecules. Each water molecule is associated both with Ca 2+ ions and with the nearest sulfate tetrahedron. Inside the layer containing Ca 2 + and SO 4 -2 ions, there are relatively strong (ionic) bonds, while in the direction of the layers containing water molecules, the bond of the layers is much weaker. Therefore, during heat treatment, gypsum dihydrate easily loses water (dehydration process). In practice, this process can be carried out varying degrees its completeness and, depending on this, to obtain gypsum binders of various modifications with different properties.
In the crystal lattice of anhydrite, sulfur ions are located at the centers of tetrahedral oxygen groups, and each calcium ion is surrounded by eight ions. For the most part anhydrite forms solid masses, but there are cubic, short-columnar, and other crystals.
Gypsum heating
Under the blowpipe, the gypsum loses water, splits and fuses into white enamel. Three effects are observed on the heating curves of gypsum:
- at 80-90°C, a certain amount of H 2 0 is released;
- at 140°C, gypsum passes into a hemihydrate;
- at a temperature of 140-220°C there is a complete release of water;
- at a temperature of 400°C, the gypsum is completely fired.
Solubility of gypsum
Gypsum has an appreciable solubility in water (about 2 g/l at 20°C). A remarkable feature of gypsum is that its solubility reaches a maximum at 37-38 °C with increasing temperature, and then drops rather quickly.
The greatest decrease in solubility is established at temperatures above 107 ° C due to the formation of "hemihydrate" - CaSO 4 . 0.5H 2 O. The solubility of gypsum increases in the presence of certain electrolytes (eg NaCl, (NH 4) 2 SO 4 and mineral acids).
Gypsum crystallizes from solution in the form of characteristic needle-shaped crystals, white or colored with impurities.
Gypsum from the Greek - plaster, is easily determined by the following properties:
- low hardness;
- abundant sublimation of water in a closed tube;
- in the flame of an alcohol lamp it turns white (cloudy) and crumbles into powder, melts into white enamel, which gives an alkaline reaction;
- relatively poorly soluble in water and acids.
Dissolution of anhydrite is a direct interaction of water and calcium sulfate, saturation occurs when the energy of the hydrated ion becomes equal to the energy of the ion in the lattice. Typically, such dissolution is accompanied by a small heat release (not always and not for all salts). Temperature is the main factor influencing this.
The process of salt dissolution also depends on the properties of the solvent (water), its salinity, composition and pH environment. Thus, the solubility of gypsum increases with an increase in the content of sodium and magnesium chloride salts in water. In distilled water, the solubility of gypsum is 2 g/l, and in highly concentrated solutions of NaCl (100 g/l) or MgCl (200 g/l), the solubility of gypsum increases to 6.5 and 10 g/l, respectively.
Gypsum is highly soluble in alkalis and hydrochloric acid. With an increase in the concentration of the alkali solution from 0.1 N. up to 1 n. the solubility of gypsum increases sharply. Thus, depending on the mineralization and composition of the solvent, the dissolution rate of gypsum can vary over a wide range, which must be taken into account when leaching it from the rock.
CaSO 4 + NaCl \u003d NaSO 4 + CaCl 2
CaSO 4 + MgCl \u003d MgSO 4 + CaCl 2
Gypsum variety
Selenite
Selenite is a fibrous difference of gypsum, a translucent mineral, stronger than alabaster. Soft, hardness 2 on the Mohs scale (easily scratched with a fingernail). As inclusions, it may contain clay, sand, rarely - hematite, sulfur, organic impurities.
Has a silky sheen. After polishing, thanks to the parallel fibers, it has a beautiful iridescent optical effect, similar to the effect of a cat's eye.
The color scheme is represented by pink, blue, yellow and reddish-pearl shades. You can also find crystal white selenite.
It is used as an ornamental stone for the manufacture of jewelry, figurines, carved art and household items. Easily sanded with sandpaper and polishes well. Products made of selenite are easily rubbed and lose their polish due to their low hardness and require re-treatment after use.
Alabaster
The name "alabastrites" comes from the name of the city of Alabaster in Egypt, where the stone was mined. Alabaster was highly prized and was used to make small containers for perfumes and vases for ointments. Cut into thin sheets, alabaster is quite transparent, so it was used to "glaze" windows.
Today, alabaster is the main raw material for the production of gypsum - a powdered binder obtained by heat treatment of natural two-water gypsum CaSO 4 . 2H 2 O at temperatures of 100°C and above.
Let me remind you that alabaster- the purest fine-grained gypsum, resembling marble in appearance, white color or light colored.
Anhydrite
Anhydrite (from other Greek "devoid of water") - anhydrous calcium sulfate. Anhydrite can be white, bluish, grayish, rarely reddish.
When water is added, it increases in volume by about 30% and gradually turns into gypsum dihydrate.
Anhydrite deposits are formed in sedimentary strata mainly as a result of dehydration of gypsum deposits.
Anhydrite is sometimes used as a cheap decorative and ornamental stone, which is intermediate in hardness between jasper, jade and agate, on the one hand, and soft selenite and calcite, on the other.
Today it is used for the production of non-fired and high-fired gypsum binders, as well as an additive for cement production.
GIPS - 1. Ca 2H 2 O. Mon. K-ly thin and thick tabular. Sp. in. owls. according to (010), Sov. according to (100) and (110). Dv. according to (100) common - dovetail. Agr.: granular, foliose, powdery, fibrous, veined, radially acicular. Colorless, white, yellowish to black. Bl. glass. Tv. 1.5-2. Oud. in. 2.32. Flexible but not stretchy. Let's noticeably dissolve in water. Forms a siege. g.p.; often in oxid. ore deposits; known hydrotherm. Formed at t 63.5 °С,
and in solutions saturated with NaCl, at t 30 °С; during the hydration of anhydrite, as well as under the influence of sulfate solutions on carbonate settlements. salty bass. Ca sulfate is deposited in the form of gypsum; in the ancients, predominantly anhydrite, less often gypsum formations are known. Miscellaneous: crystalline G.; fiber., or; grainy or; sandy - poikilitic. 2. Siege. g. p., consisting mainly of m-la gypsum and included in gr. halogen items. According to the conditions of G.'s formation, it can be primary (actually precipitated), formed chemical. precipitation in salted bass. in the early stages halogenesis, or secondary. The latter include the widely developed gypsum that occurs during the hydration of anhydrite in the near-surface zone: plaster hats; metasomatic gypsum (chip arr. according to carbonate deposits), etc. gypsum is used in raw and baked form in the construction industry, in the production of binders, plaster and molding gypsum, estrichgypsum, gypsum cement, and for the production of sulfuric gypsum.
Geological dictionary: in 2 volumes. - M.: Nedra. Edited by K. N. Paffengolts et al.. 1978 .
(from Greek gypsos -, lime * a. gypsum; n. gypsum; f. gypse, pierre a platre; and. yeso) -
1)
sulfate class mineral, Ca (SO 4) 2H 2 O. B pure form contains 32.56% CaO, 46.51% SO 3 and 20.93% H 2 O. Mechanical. impurities ch. arr. in the form of organic and clay substances, sulfides, etc. It crystallizes in a monoclinic syngony. At the base of the crystalline structures - double from anionic groups (SO 4) 2- linked by Ca 2+ cations. Crystals are tabular or prismatic, form twins, the so-called. dovetail. very perfect. Aggregates: granular, foliose, powdery, concretions, fibrous veinlets, radial-acicular. Pure G. is colorless and transparent; in the presence of impurities, it has a gray, yellowish, pinkish, brown to black color. Glass luster. Tv. 1.5-2. 2300 kg / m 3. Let's noticeably dissolve in water (2,05 g/l at 20 °C). By origin ch. arr. chemogenic. It precipitates at t 63.5°C, and in solutions saturated with NaCl, at a temperature of 30°C. When means. increasing salinity in drying seas. in lagoons and salt lakes, anhydrous sulphate, anhydrite, begins to precipitate instead of sulphate; similarly, it occurs when sulphide is dehydrated. Hydrogen, which forms in low-temperature sulfide deposits, is also known. Varieties: selenite - translucent fibrous aggregates, cast in reflected light with a beautiful silky sheen; gypsum spar - lamellar G. in the form of transparent crystals of a layered structure, etc.
.
2)
Sedimentary mountain. breed, consisting in the main. from the mineral G. and impurities (anhydrite, iron hydroxides, sulfur, etc.). According to the conditions of G.'s formation, it can be primary, formed by chemical. deposition in salinized basins at the beginning. stages of halogenesis, or secondary, arising from the hydration of anhydrite in the near-surface zone - gypsum hats, metasomatic. G. and others. The quality of gypsum raw materials is determined in the main. the content of calcium sulfate dihydrate (CaSO 4 2H 2 O), a cut in decomp. varieties of gypsum stone varies from 70 to 90%.
G. is used in raw and burnt form. 50-52% of gypsum stone mined in the USSR is used to produce gypsum binders decomp. purpose (GOST 195-79), obtained by firing natural G., 44% G. - in the production of Portland cement, where G. is used as an additive (3-5%) to regulate the setting time of cement, as well as for the production of special. cements: gypsum-alumina expanding cement, tension cement, etc. 2.5% G. consumes s. x-in in the production of nitrogen fertilizers (ammonium sulfate) and for gypsum saline soils; in non-ferrous metallurgy G. is used as a flux, in the main. when smelting nickel; in paper production - as a filler, preim. in the highest grades of writing papers. In some countries (Great Britain, etc.), G. is used for the production of sulfuric acid and cement. G.'s ability to be easily processed, well-received polishing and usually high decorative properties make it possible to use it as a marble imitator in the production of facing slabs for inside. building decoration and as a material for decomp. crafts.
In the south districts of the USSR in Nar. x-ve used clay gypsum with a content of CaSO 4 ·2H 2 O from 40 to 90%. Loose rock, consisting of G., and sand, called. earthy G., and in Transcaucasia and Wed. Asia - "" or "ganch". These rocks in their raw form are used for gypsuming soils, in burned form - for plastering, as an astringent.
In the USSR, the largest deposits are located in the Donbass, Tula, Kuibyshev, Perm regions RSFSR, in the Caucasus and in Wed. Asia. At 150 deposits of G. and 22 deposits of clay-gypsum, drywall and ganch, they were explored according to the industrial. categories reserves 4.2 billion tons (1981). There are 11 deposits, gypsum reserves in which exceed 50 million tons (including Novomoskovskoe - 857.4 million tons).
Mining deposits are developed by quarries (Shedoksky, Saurieshsky mines, etc.) and mines (Novomoskovsky, Artyomovsky, Kamskoye Ustye, etc.). In the USSR, 42 deposits of gypsum and anhydrite and 6 deposits of gypsum-bearing rocks are exploited with an annual production of approx. 14 million tons (1981), of which 60.2% - on the territory. RSFSR and 15.8% - Ukrainian SSR. Most large enterprises- "Novomoskovsky" (2.33 million tons), "Ergachinsky", "Artyomovsky" (1.0 million tons each) and "Zalarinsky" (0.85 million tons).
The world's proven reserves of gas are estimated at 2.2 billion tons: 0.6 billion tons in the USA; 0.375 billion tons in Canada; 0.825 billion tons in European countries (in France, Germany, Spain, Italy, Yugoslavia and Greece); 0.09 billion tons in Asian countries; 0.07 billion tons each in Mexico and African countries. G.'s resources are many times greater than the proven reserves. World mining G. among the capitalist. countries is 70 million tons (1978), of which the United States accounts for 20% (13.5 million tons), Canada - 11% (7.9 million tons). In Europe, 30.7 million tons are mined, in Asia - 11.9 million tons. Literature: Vinogradov B. N., Raw material base industry of binders of the USSR, M., 1971; Vikhter Ya. I., Production of gypsum binders, 4th ed., M., 1974. Yu. S. Mikosha.
Mountain Encyclopedia. - M.: Soviet Encyclopedia. Edited by E. A. Kozlovsky. 1984-1991 .
Synonyms:See what "gypsum" is in other dictionaries:
gypsum- gypsum, and ... Russian spelling dictionary
gypsum- gypsum / ... Morphemic spelling dictionary
Gypsum- - (from the Greek gypsos - chalk, lime) - 1) G. natural - a mineral, aqueous calcium sulfate CaSO4 * 2H2O. Color white, yellowish, cream; often colorless. Tv. in mineralogy, scale 1.5 - 2; dense 2300 kg/m3. Consisting Ch. arr… Encyclopedia of terms, definitions and explanations of building materials- (Turkmenistan). Gypsum (from the Greek gypsos chalk, lime), 1) mineral, aqueous calcium sulfate. Colorless, gray crystals, aggregates. Hardness 1.5 2; density 2.3 g/cm3. Varieties: gypsum spar (translucent crystals); satin spar, or ... ... Illustrated Encyclopedic Dictionary
GYPSUM- Gypsum, calcium sulphate, Calcium sul furicum, CaS04 + 2H20, white soft, easily powdered mineral found in nature in the form of large deposits; synthetically obtained by the action of sulfuric acid or its water-soluble salts ... ... Big medical encyclopedia
- (from Greek gypsos chalk lime), 1) a mineral of the sulfate class, CaSO4.2H2O. Colorless, white, gray crystals, aggregates. Hardness 1.5 2; density 2.3 g/cm³. Varieties: gypsum spar (translucent crystals); satin spar, or Ural ... ... Big Encyclopedic Dictionary
Gypsum, plaster, husband. (Greek gypsos). 1. only units Sulphuric lime crystalline mineral salt b. h. white or yellow color, use among other things, in surgery and serving as a material for sculptural work (miner.). 2. Sculptural cast from ... ... Dictionary Ushakov
For many people who are inexperienced in repair and construction matters, the question often arises: what is the difference between such Construction Materials like plaster and alabaster? And why is it written on the top of the bags “gypsum plaster”, and below - “alabaster”?
In order not to get lost in terms, you need to figure out what gypsum and alabaster really are, whether there are differences between them and, if so, which ones.
Gypsum - origin, application
Gypsum is a dry composition made on the basis of a natural mineral - gypsum stone. The mineral is calcium sulfate dihydrate - CaSO4 2H2O with impurities in the form of oxides of silicon, aluminum and iron.
Gypsum is a mineral of sedimentary origin. In nature, it is most often found in the form of elongated prism-shaped crystals, although it sometimes forms in the form of dense tablet or scaly aggregations. The mineral is quite soft, easy to grind.
Large deposits of gypsum stone are located in countries such as Iran, USA, Canada, Turkey, Spain. In Russia, deposits of this rock are located in the Kama and Volga regions, Tatarstan, on the western slopes Ural mountains and in the Krasnodar Territory.
An astringent is obtained from a natural mineral - in fact, the gypsum that we all know. It is a powder of white, cream or grayish color (depending on the impurities present), which, when mixed with water, turns into a plastic mass that quickly hardens in air.
The method of using ground gypsum depends on what exactly it is planned to be used for:
- "raw" gypsum is used in medicine to fix fractures, as well as in agriculture - it is scattered in the fields to normalize the acidity of the soil;
- in the form of "building gypsum" it is used during repair and finishing works, for the production of wall slabs and blocks, cornices, stucco moldings.
Also, the mineral is widely used in paper and chemical industry: in the production of cement, sulfuric acid, glazes and paints.
Natural gypsum is fibrous and granular. For the production of alabaster, fine-grained gypsum is used - alabaster. Construction alabaster has a finer grinding and is the same calcium sulfate, but not dihydrate, but semi-hydrous - CaSO4 0.5H2O. It is obtained by roasting crushed natural alabaster at temperatures up to 180 degrees.
Thus, the alabaster that we purchase at the hardware store is broad sense is gypsum, but not every gypsum can be called alabaster.
Building gypsum has the following characteristics:
- Density (true) is 2.6 - 2.76 g / cu. cm. At the same time, in a loose-filled form, the density is 0.85 - 1.15 g / cu. cm, and in compacted - 1, 245 - 1.455 g / cu. cm.
- Gypsum products have high fire resistance - they are destroyed only after 6-8 hours of exposure high temperature. Designs withstand heating up to 600-700 degrees without destruction.
- The compressive strength of building gypsum is 4-6 MPa, high-strength gypsum - 15-40 MPa.
- Gypsum and products made from it do not conduct heat well, its heat transfer coefficient in the temperature range from 15 to 45 degrees is only 0.259 kcal/m deg/hour.
- Drying speed. After mixing with water, the gypsum mortar begins to set after 4 minutes and within the next half hour it completely hardens. Therefore, you need to work with such a solution very quickly.
Grades and properties of building gypsum
The normative document regulating the properties and quality of building gypsum binders is GOST 125-79. The industry produces 12 brands of alabaster, differing in compressive fracture strength.
The indicators are shown in the table:
| Gypsum brand | Tensile strength of beam specimens 40 × 40 × 160 mm in size at the age of 2 hours,MPa, not less | |
| compression | bend | |
| G-2 | 2 | 1,2 |
| G-3 | 3 | 1,8 |
| G-4 | 4 | 2,0 |
| G-5 | 5 | 2,5 |
| G-6 | 6 | 3,0 |
| G-7 | 7 | 3,5 |
| G-10 | 10 | 4,5 |
| G-13 | 13 | 5,5 |
| G-16 | 16 | 6,0 |
| G-19 | 19 | 6,5 |
| G-22 | 22 | 7,0 |
| G-25 | 25 | 8,0 |
An important indicator is the setting time of the binder.
Depending on it, the following types of building gypsum are distinguished:
- A - fast-hardening (beginning no earlier than 2 minutes, end - no later than 15 minutes).
- B - normally hardening (setting begins no earlier than 6 minutes, end - no later than 30 minutes).
- B - slowly hardening (the beginning of setting is not earlier than 20 minutes, the end is not standardized).
The degree of grinding is also normalized:
Thus, according to the brand of binder, all its main characteristics can be determined.
For example, the bag says: Г-6 В II.
This means that we have a material with the following characteristics:
- strength not less than 6 and not more than 7 MPa;
- slowly hardening;
- medium grind.
Varieties of gypsum
Gypsum binders are used not only in pure form, but also with various additives that allow changing their properties.
Currently on sale you can find gypsum of the following varieties:
- Construction - for the production of gypsum building materials and for carrying out plastering works. Such material is good because it does not form cracks when dried. Lime is often added to it, which gives the mixture plasticity. The material is mainly used for interior decoration dry rooms.
- High-strength - a binder with large crystals, providing the final product with less porosity and, accordingly, greater strength. This material used for the construction of fireproof partitions, molds for the production of faience and porcelain sanitary ware. It is also used in traumatology and dentistry.
- Polymer gypsum is a binder with the addition of polymers. Often used in traumatology. Dressings with such gypsum are much lighter than ordinary gypsum ones, allow the skin to breathe, are not afraid of moisture, are permeable to X-rays (they allow you to control the process of bone fusion).
- Sculptural - the most high-strength gypsum, practically free of impurities. The material has a high degree whiteness and is used to make figurines. Sculptures, souvenirs, as well as in the automotive and aviation industries. This binder is the basis of dry putty mixtures.
- Acrylic gypsum - obtained by adding water-soluble acrylic resin to the binder. Externally, it is practically indistinguishable from ordinary gypsum, but much lighter. Because of this, it is often used for ceiling moldings. The material is frost-resistant and has low water absorption, therefore it can be used for work on building facades.
Thus, alabaster is one of the varieties of gypsum, which is mainly used in construction. It has greater hardness than natural gypsum, but is less widely used.
