Advantages and technical characteristics of quartz sand. Glass - what is it and how is it produced? glass properties

Quartz- one of the most common minerals in the earth's crust, a rock-forming mineral of most igneous and metamorphic rocks. Free content in the earth's crust 12%. Included in other minerals in the form of mixtures and silicates. In total, the mass fraction of quartz in the earth's crust is more than 60%. It has many varieties and, like no other mineral, is diverse in color, in forms of occurrence, and in genesis. It occurs in almost all types of deposits.
Chemical formula: SiO 2 (silicon dioxide).

See also:

STRUCTURE

trigonal syngony. Silica, the most common form of which in nature is quartz, has a developed polymorphism.
Two main polymorphic crystalline modifications of silicon dioxide: hexagonal β-quartz, stable at a pressure of 1 atm. (or 100 kN / m 2) in the temperature range of 870-573 ° C, and trigonal α-quartz, stable at temperatures below 573 ° C. It is α-quartz that is widespread in nature, this stable at low temperatures the modification is usually referred to simply as quartz. All hexagonal quartz crystals found under normal conditions are paramorphoses of α-quartz after β-quartz. α-quartz crystallizes in the trigonal trapezohedron class of the trigonal syngony. The crystal structure is of a frame type, built of silicon-oxygen tetrahedra arranged helically (with a right or left screw stroke) with respect to the main axis of the crystal. Depending on this, right and left structural-morphological forms of quartz crystals are distinguished, which are externally distinguished by the symmetry of the arrangement of some faces (for example, a trapezohedron, etc.). The absence of planes and a center of symmetry in α-quartz crystals determines the presence of piezoelectric and pyroelectric properties in it.

PROPERTIES

In its pure form, quartz is colorless or has a white color due to internal cracks and crystal defects. Impurity elements and microscopic inclusions of other minerals, mainly iron oxides, give it a wide variety of colors. The reasons for the coloration of some varieties of quartz have their own specific nature.
Often forms twins. It dissolves in hydrofluoric acid and alkali melts. Melting point 1713-1728 °C (due to the high viscosity of the melt, it is difficult to determine the melting point, there are various data). dielectric and piezoelectric.

It belongs to the group of glass-forming oxides, that is, it can be the main component of glass. One-piece pure silica quartz glass is obtained by melting rock crystal, vein quartz and quartz sand. Silicon dioxide has polymorphism. Stable at normal conditions polymorphic modification - α-quartz (low-temperature). Accordingly, the high-temperature modification is called β-quartz.

MORPHOLOGY

Crystals are usually in the form of a hexagonal prism, at one end (rarely both) crowned with a six- or triangular pyramidal head. Often the crystal gradually narrows towards the head. On the faces of the prism, transverse hatching is characteristic. Most often, crystals have an elongated prismatic shape with the predominant development of hexagonal prism faces and two rhombohedra forming the crystal head. More rarely, crystals take the form of a pseudohexagonal dipyramid. Outwardly regular quartz crystals are usually complexly twinned, most often forming twin sections according to the so-called. Brazilian or Dauphinean laws. The latter arise not only during crystal growth, but also as a result of internal structural rearrangement during thermal β-α polymorphic transitions accompanied by compression, as well as during mechanical deformations.
In igneous and metamorphic rocks quartz forms irregular isometric grains intergrown with grains of other minerals; its crystals are often encrusted with voids and tonsils in effusives.
In sedimentary rocks - concretions, veinlets, secretions (geodes), brushes of small short-prismatic crystals on the walls of voids in limestones, etc. Also fragments various shapes and sizes, pebbles, sand.

VARIETIES OF QUARTZ

Yellowish or shimmering brownish-red quartzite (due to inclusions of mica and iron mica).
- layered-banded variety of chalcedony.
- violet.
Bingemite - iridescent quartz with inclusions of goethite.
Bull's eye - deep crimson, brown
Volosatik - rock crystal with inclusions of fine acicular crystals of rutile, tourmaline and / or other minerals that form acicular crystals.
- crystals of colorless transparent quartz.
Flint - fine-grained cryptocrystalline aggregates of silica of variable composition, consisting mainly of quartz and, to a lesser extent, chalcedony, cristobalite, sometimes with the presence of a small amount of opal. Usually found in the form of nodules or pebbles resulting from their destruction.
Morion is black.
Overflow - consist of alternating layers of microcrystals of quartz and chalcedony, they are never transparent.
Prazem - green (due to inclusions of actinolite).
Prasiolite - onion-green, obtained artificially by calcining yellow quartz.
Rauchtopaz (smoky quartz) - light gray or light brown.
Rose quartz - pink.
- cryptocrystalline fine-fiber variety. Translucent or translucent, color from white to honey-yellow. Forms spherulites, spherulitic crusts, pseudostalactites or continuous massive formations.
- lemon yellow.
Sapphire quartz is a bluish, coarse-grained aggregate of quartz.
Cat's eye - white, pinkish, gray quartz with a light sheen effect.
Hawkeye is a silicified aggregate of bluish-gray amphibole.
Tiger's eye - similar to hawk's eye, but golden brown in color.
- brown with white and black patterns, red-brown, brown-yellow, honey, white with yellowish or pinkish layers. Onyx is especially characterized by plane-parallel layers of different colors.
Heliotrope is an opaque dark green variety of cryptocrystalline silica, mostly fine-grained quartz, sometimes with an admixture of chalcedony, oxides and hydroxides of iron and other minor minerals, with bright red spots and stripes.

ORIGIN

Quartz is formed by various geological processes:
Directly crystallizes from acidic magma. Quartz contains both intrusive (granite, diorite) and effusive (rhyolite, dacite) rocks of acidic and intermediate composition; it can occur in igneous rocks of basic composition (quartz gabbro).
It often forms porphyritic phenocrysts in felsic volcanic rocks.
Quartz crystallizes from fluid-enriched pegmatite magmas and is one of the main minerals in granitic pegmatites. In pegmatites, quartz forms intergrowths with potassium feldspar (pegmatite proper), the inner parts of pegmatite veins are often composed of pure quartz (quartz core). Quartz is the main mineral of apogranitic metasomatites - greisens.
During the hydrothermal process, quartz and crystal-bearing veins are formed, special meaning have alpine-type quartz veins.
Under surface conditions, quartz is stable and accumulates in placers of various genesis (coastal-marine, eolian, alluvial, etc.). Depending on the various conditions formations, quartz crystallizes in various polymorphic modifications.

APPLICATION

Quartz is used in optical devices, in ultrasound generators, in telephone and radio equipment (as a piezoelectric), in electronic devices (“quartz” in technical slang is sometimes called a quartz resonator - a component of devices for stabilizing the frequency of electronic generators). AT large quantities consumed by the glass and ceramic industries (rock crystal and pure quartz sand). It is also used in the production of silica refractories and quartz glass. Many varieties are used in jewelry.

Quartz single crystals are used in optical instrumentation for the manufacture of filters, prisms for spectrographs, monochromators, lenses for UV optics. Fused quartz is used to make special chemical glassware. Quartz is also used to obtain chemically pure silicon. Transparent, beautifully colored varieties of quartz are semi-precious stones and are widely used in jewelry. Quartz sands and quartzites are used in the ceramic and glass industry

Quartz (English Quartz) - SiO 2

CLASSIFICATION

PHYSICAL PROPERTIES

The main components of a huge number of building materials are natural components, which are characterized by the required properties and are in sufficient quantities for production on an industrial scale. Quartz sand is considered one of the common natural minerals and is used in all areas of construction activity. allowed him to gain such high popularity.

Quartz sand is one of the most common building materials and is used in various areas of construction.

Before you begin to get acquainted with the chemical properties of the material, it is worth knowing what they are provided with. The main component of quartz sand is silicon dioxide, which is represented by quartz. Its formula is as follows: SiO2. It contains iron oxides, organic impurities, clay and other metals. The content of quartz in the primary mineral, as a rule, is 93-95%.

The principle of operation of building compounds used in the production of plates and blocks is based on the chemical interaction of the components. The resulting inorganic chains guarantee the necessary material parameters.

Silicon dioxide is an acidic oxide, which causes interaction with aluminum and calcium compounds, which are found in limestone and clay. The process is able to proceed when the wet composition dries or at the time of thermal baking.

Types of quartz sand

Quartz sand can be represented by natural and artificial varieties, which differ in the method of extraction. The first species is ubiquitous in nature, it can be found at the bottom water basins and deep in the soil. The fraction of most of its grains can vary within 0.2-1 mm.

There are several ways to extract quartz sand, one of them is quarrying, which acts as the leading method. If mining is carried out above sea level, the material is called mountainous. The type of quarry sand is characterized by pointed shapes and a rough surface, which makes it a valuable building material. After mining, sand can be further processed, which includes screening, washing and drying. Another way to extract quartz sand is the development of water basins, while the particles are washed out and are clean.

Sea sand is not so valuable due to the increased content of mineral impurities. This material is smooth.

Quartz sand has another variety - artificial. But, despite the name, the material is of natural origin, because it is originally found as large crystals. In order for quartz crystals to turn into sand, mechanical action is used, then the fragments are crushed.

It is possible to single out some areas of classification of sand based on quartz, for example, by fractional composition. Thus, quartz can be dusty, the fraction of the material is less than 0.1 mm; fine-grained with a grain size ranging from 0.1 to 0.25 mm; medium - fraction within 0.25-0.5 mm; coarse-grained - 0.5-1 mm, in rare cases, the grain size can reach 3 mm.

Sea sand contains a large number of minerals, so it is rarely used in construction.

Quartz sand can also be classified by enrichment. So, it can be unenriched and enriched. The first option is the mineral in its original form, not subject to processing to increase the amount of silicon dioxide in the composition. The second option is represented by sand, which contains a certain amount of quartz content increased by a certain percentage, which can be achieved by eliminating a number of impurities. So, white material does not contain organic compounds, clay impurities, iron oxides, which can be achieved after sifting, washing and drying.

Quartz sand can also be classified according to enrichment technology.

The initial enrichment step involves fractionation and washing. The next step may be gravitational enrichment, which aims to separate the components of the composition by density.

The particles may have different colors. There is natural and dyed material. Natural is characterized by shades from pale yellow to brownish yellow. And for artificial coloring, stable paints based on synthetic binders are used.

Various specifications have sands classified according to the degree of preparation. Thus, the production may require fractionated material, dry or calcined, the latter of which is characterized by the absence of moisture in the composition, which is achieved by calcination.

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Normalization of characteristics

The main regulatory document is GOST 2138-91. The document reflects the requirements for the leading characteristics and quality parameters. So, 5 groups of material can be distinguished, each of which should contain a specified amount of clay in the range of 0.2-2.0%. The content of silicon dioxide in the sand should vary from 93 to 99%, a material with a certain content of this component will correspond to the group K1-K5.

The material can also have its own uniformity coefficient, with an increase in the value, the sand mixture is characterized by greater uniformity. Sand also has a certain fractional composition, which reflects the dimensions of the particles. GOST and humidity indicators are taken into account. Dry formulations contain a maximum of 0.5% moisture, while wet formulations should not contain more than 4.0%. As for raw, this figure does not exceed 6.0%.

What is the melting point of sand please?

1. Melting temperature
   From Wikipedia, the free encyclopedia
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   Temperaturémelting&solidificatiońtemperature is the temperature at which a solid crystalline body makes a transition to a liquid state and vice versa. At the melting point, a substance can be in both a liquid and a solid state. When adding additional heat, the substance will go into a liquid state, and the temperature will not change until all the substance in the system under consideration has melted. When removing excess heat (cooling), the substance will go into a solid state (freeze) and until it solidifies completely, the temperature will not change.

   Melting/solidification point and boiling/condensing point are considered important physical properties substances. The solidification temperature coincides with the melting point only for a pure substance. Special thermometer calibrators are based on this property for high temperatures. Since the pour point of a pure substance, such as tin, is stable, it is enough to melt and wait until the melt begins to crystallize. At this time, under the condition of good thermal insulation, the temperature of the solidified ingot does not change and exactly coincides with the reference temperature indicated in the reference books. Mixtures of substances do not have a melting / solidification temperature at all, and make a transition in a certain temperature range (the temperature of the appearance of the liquid phase is called the solidus point, the temperature of complete melting is the liquidus point). Since it is impossible to accurately measure the melting point of such substances, special methods are used (GOST 20287 and ASTM D 97). But some mixtures (of eutectic composition) have a certain melting point, as pure substances.
   Amorphous (non-crystalline) substances, as a rule, do not have a clear melting point, the viscosity of such substances decreases with increasing temperature, and the lower the viscosity, the more liquid the material becomes.
   For example, the usual window glass is a supercooled liquid. Over several centuries, it becomes clear that at room temperature the glass on the window slides down under the influence of gravity and becomes thicker at the bottom. At a temperature of 500-600, the same effect can be observed for several days.

   Since the volume of the body changes insignificantly during melting, the pressure has little effect on the melting point. The dependence of the phase transition temperature (including melting and boiling) on ​​pressure for a one-component system is given by the Clausius-Clapeyron equation. Melting point at normal atmospheric pressure(1013.25 hPa, or 760 mm mercury column) is called the melting point.

   Melting points of some important substances:

   sand (melting point (tmelt) = 1710 C), clay (tmelt from 1150 to 1787 C),
   melting point C
   hydrogen #8722;259.2
   oxygen #8722;218.8
   nitrogen #8722;210.0
   ethyl alcohol #8722;114,5
   ammonia #8722;77.7
   mercury #8722;38.87
   ice (water) +0
   benzene +5.53
   cesium +28.64
   sucrose +185
   saccharin +225
   tin +231.93
   lead +327.5
   aluminum +660.1
   silver +960.8
   gold +1063
   iron +1535
   platinum +1769.3
   corundum +2050
   tungsten +3410

2. 17131728C if the sand is pure quartz
   http://ru.wikipedia.org/wiki/Sand
   http://ru.wikipedia.org/wiki/Quartz

Majority basis building materials are natural components that have the necessary properties and are in sufficient quantity for industrial production. Quartz sand is one of the most common natural minerals and is used in all areas of construction.

What provides the chemical properties of the material

The main component of quartz sand is silicon dioxide (quartz). Its formula is SiO2. It may also contain organic impurities, clay, oxides of iron and a number of other metals. The content of quartz in the original mineral is usually not less than 93-95%.

The principle of operation of building mixtures used to obtain building blocks and slabs is based on the chemical interaction of the components. The resulting inorganic chains provide the required parameters of the material.

Silicon dioxide is an acidic oxide, therefore it reacts with calcium and aluminum compounds found in limestone and clay. The interaction can proceed both during the drying of the wet mixture and during thermal baking.

Varieties of quartz sand and its extraction

There are natural and artificial varieties of sand, which differ in the method of extraction.

natural natural

This type of sand is ubiquitous in nature and is found at the bottom of water basins and in the composition of the soil. Most of its grains are 0.2 to 1 mm in size.

There are several ways to extract quartz sand:

• quarrying- is the main way. If mining is carried out above sea level, then the resulting sand is called mountain sand. Varieties of soil sand are extracted during the development of soil on the plains. The appearance of quarry sand is characterized by pointed shapes and often a rough surface, which makes it a valuable building material. The extracted sand can be subjected to additional processing - screening, washing and drying. The more stringent the requirements for sand properties in any industry, the more thorough the preparation required. In the construction of small structures, sand is usually not exposed to any impact and is supplied directly from the place of its extraction;
• development of water basins– the sand is washed out by the dredger and is characterized by high purity provided by natural washing. Mining is carried out in riverbeds, lakes, as well as marine areas. Sea sand is somewhat less valuable due to the higher content of mineral impurities. River sand has a smooth shape - under a microscope, the grains of sand resemble sea pebbles. The use of smooth (rounded) sands is common in self-leveling mixtures - sand grains do not cling to each other.

This is how natural quartz sand looks like in the photo

artificial sand

Despite the name, the mineral has a natural origin, but initially it is in the form of large crystals. To turn quartz crystals into sand, mechanical action (explosion) is used, after which the fragments are crushed.

Ways to classify quartz sand

The starting point in the classification system is the properties of the material and how it is prepared. There are the following areas of classification of quartz sand:

By size (fractional composition)

The numerical expression is the average value of particle sizes or their size range (fraction):

1. pulverized quartz - represents a fraction of less than 0.1 mm (sifted into a sieve with a pore diameter of 0.1 mm) and is usually found when crushing quartz crystals;
2. fine-grained sand - a fraction of 0.1-0.25 mm;
3. medium sand - fraction 0.25-0.5 mm;
4. coarse sand - a fraction of 0.5-1 (rarely up to 3) mm.

For enrichment

Quartz sand is divided into unenriched and enriched sand:

• raw sand is the original mineral that has not been treated to increase the silica content;
• enriched sand contains a few percent increased quartz content, obtained by removing most of the impurities. Thus, white quartz sand is purified from organic compounds, iron oxides and clay impurities by sifting, washing and drying.

Due to the peculiarities of production, the main technical characteristics of the material obtained also differ. This, in turn, affects the possibility of further .

enrichment technology

The high purity of the quartz mixture is necessary requirement in a number technological processes. The initial enrichment stage includes fractionation and washing - with their help, the coarsest impurities are removed.

The next step is to use special technologies, such as:

• gravity enrichment- the main method, the essence of which is to separate the components of the mixture by density. Lighter particles are carried away water stream, while the heavy ones settle to the bottom of the apparatus. The gravitational effect can be enhanced by centrifugation or the addition of chemicals that change the wettability of the sand components;
• electrical and magnetic separation- represents the impact of electric current and magnetic field leading to the separation of some impurities. So, the magnetic effect is especially effective when cleaning from iron particles with magnetic properties.

The parameters of the enriched sand fundamentally affect the quality of the work performed. Sand mixtures with the best properties are produced only by certified enterprises using standard technologies.

By color

It is natural and dyed. Natural quartz sand is pale yellow to brownish yellow in color. Artificial dyeing is carried out with stable paints based on synthetic binders, allowing you to create original multi-color ornaments from sand. Such sand can be colored and white.

According to the degree of preparation

Depending on the technological requirements, sand can be produced in the following varieties:

1. fractionated- represents a specific fraction of sand, the size of which is limited by technical regulations;
2. dry- air-dried. Together with fractionated sand, it can be used as a working medium for sandblasting machines;
3. calcined sand- completely dehydrated by calcination. Heating significantly above 100 °C ensures the desorption of moisture even from the deep pores of quartz. Such sand is used in ready-made building mixtures stored long time- even a slight moisture content can render the entire mixture unusable;
4. rounded quartz sand- has less abrasive properties, therefore it is suitable for delicate applications, for example, sandboxes on playgrounds;
5. molding quartz sand- used to produce cast quartz products and differs a high degree enrichment.

Production and extraction of quartz sand

On the territory of Russia there is a significant number large deposits quartz sand. The most famous are the Chulkovskoe (Moscow region), Kozlovskoe (Bryansk region), Elshanskoe (Volgograd region), Berezichskoe (Kaluga region) deposits and a number of others.

Differences of quartz construction sand, extracted from these places, are initially high quality parameters and higher cost. It is important to understand that the properties of sand from the nearest quarry will be quite sufficient for the construction of small summer cottages, so you should not overpay. If the goal is to build a large mansion, then saving on the quality of sand can negatively affect the durability of the house.

This is how quartz sand is mined on a special production line:

What are the characteristics of sand

The main regulatory document is GOST 2138-91, there are also other regulatory documents ( GOST 22551 77, GOST 51641 2000, 8736 93). They reflect the requirements for the main quality parameters and properties, namely:

1. the content of the clay component. Allocate 5 groups with established amounts of clay from 0.2 to 2.0%;
2. silicon dioxide content - from 99% to 93%, corresponding to groups from K1 to K5;
3. coefficient of uniformity, reflecting the variation in particle size relative to the average (in %). The higher the value, the more uniform the sand mixture. In total, there are five groups (from O1 to O5), differing in the coefficient of uniformity (from 80 to 50%);
4. fraction composition. This parameter reflects the average particle size of quartz sand: up to 0.14 mm; 0.14-0.18 mm, 0.19-0.23 mm, 0.24-0.28 mm, more than 0.28 mm;
5. humidity. Dry sands contain no more than 0.5% moisture, wet - no more than 4.0%, wet - no more than 6.0%;
6. in the composition of the sand, the content of metal oxides, the surface area of ​​the grains, their shape, gas permeability, as well as the weight loss upon ignition are also normalized.

Quality sand must have a certificate of compliance with the specified standards.

Operational properties of quartz sand

Material parameters that affect the quality of work and determine the scope of application include:

• bulk density - is about 1300-1500 kg / m3;
• true density - is in the range of 2600-2700 kg / m3. The value of true density is used in calculating the volume of cement or concrete mortar obtained by mixing the components;
• the thermal conductivity of quartz sand is about 0.30 W / (m? ° C). The shape and dimensions of sand granules have a significant effect on the heat-insulating properties - the denser their arrangement and the smaller the gaps, the higher the thermal conductivity coefficient;
• melting temperature - the maximum working temperature of quartz sand is estimated at 1050 ° C, which is quite enough for any construction work. When casting quartz products, temperatures of 1700 °C and above are used.
• normal quartz sand in a loose state has a bulk density of 1,500 kg/m3 and a bulk density of 1,600 kg/m3.

Advantages and disadvantages of the material - general assessment

Quartz sand is an almost indispensable component in many applications, and technologies with its participation have been worked out to perfection. For practicality, the material receives a "5".

The appearance of sand is familiar from childhood, and sand playgrounds are often associated with the beach and relaxation - for appearance also put a solid "5".

Despite the massive use of sand, its fine dust can lead to chronic diseases at the builders. For environmental friendliness, the material receives a "4".

The cost of sand is comparable to the cost of other building materials. Lacking special advantages in price, quartz sand deserves a rating of "4".

The approximate cost of various fractions of quartz sand is shown in the table:

Along with clay and limestone, quartz sand is one of the most important and necessary components for production and everyday life. The variety of material properties provides a wide range of applications. The presence of sand pits near the construction site significantly reduces the cost of building a house.