Industrial types of diamond and graphite deposits

The deposits of diamonds are divided into alluvial and indigenous, among which types and subtypes are distinguished, differing in terms of occurrence, the shape of ore bodies, concentrations, quality and stocks of diamonds, extraction and enrichment conditions.

Indigenous deposits of kimberlite-type diamonds are the main objects of operation throughout the world. Of these, about 80% of natural diamonds are mined. According to diamond stocks and sizes, they are divided into unique, large, medium and small. With the highest profitability, the upper horizons of the unique and large deposits emerging on the day surface are worked out. They contain the main reserves and forecasted diamond resources of individual diamondiferous kimberlite fields. Kimberlites are “volcanic vents” filled with breccias. Breccia consists of debris and xenoliths surrounding and deposited from above rocks, from debris of rocks taken from depths of 45-90 km and more.

The cement is a volcanic material, tuffs of alkaline-ultra-basic composition, the so-called kimberlites and lamproites. Kimberlite pipes are located on platforms, lamproite – in their folded frame. The time for the formation of tubes varies from Archaean to Cenozoic, and the age of diamonds, even the youngest, is about 2-3 billion years. The formation of the tubes is associated with a breakthrough upward through narrow channels at a high pressure, at a depth of more than 80 km, at a temperature of about 1000 alkaline-ultrabasic melts. Most of the well-studied kimberlite bodies have a complex structure; In the most simplified case, the structure of the tube involves two main varieties of rocks formed during two consecutive phases of introduction: breccia (1st stage) and massive “large-porphyry” kimberlite (2nd stage). In the structure of some kimberlite pipes, kimberlite dikes and veins associated with tubes were also identified. Blind bodies, formed by portions of kimberlite magma, did not reach the surface of the day. Deposits associated with dikes and veins of kimberlites are usually classified as small, less often average in diamond reserves. In many cases, a breakthrough has reached the paleo-surface, but many explosion tubes can be “blind” and have not yet been eroded by erosion .e. Lie somewhere in the depths. But even on the surface of the Earth there are places where there are enough pressures to form a diamond. These are the places of impact of meteorites, where the diamond is found not only in the Earth, but also in a number of meteorites themselves.

The velocity of the breakthrough magma probably could be very large, about 800 km / h, magma tore and carried up fragments of different composition. If they contained diamonds, the tube became diamond-bearing. Diamonds themselves are the most stable polymorphic modification of carbon in the deep zones of the Earth.

Lamproite type of diamond deposits was discovered relatively recently (1976) in Western Australia, where a large Argyll deposit is being exploited. In their structure, lamproite deposits are generally similar to kimberlite deposits. Judging by the Argyll exploration data, lamproite tubes somewhat wedge to a depth where they pass into dikes. The system of mining of these deposits and the technology of enrichment are the same as those at kimberlite objects.

Kimberlite-lamproite type is represented by a diamond deposit in the Arkhangelsk region, where the content of indicator minerals is significantly lower than in “classical” kimberlites, the overwhelming majority of diamonds are represented by the curved forms.

Ring impact structures ranging in size from the first to hundreds of kilometers are associated with super-powerful explosive processes, the source of which, according to different researchers, was either extraterrestrial (the fall of large celestial bodies) or endogenous in nature. In Russia, one deposit of this type was discovered – Popigajskoe on the eastern slope of the Anabar crystalline massif. In terms of ore reserves and the content of diamonds, the deposit exceeds hundreds of times the largest in kimberlites. However, diamonds in impact fields are encased in strong dense effusive rocks and are represented exclusively by technical varieties with admixture of lonsdaleite (a polymorphic modification of carbon, found in the form of plates alternating with graphite, but located perpendicular to its plane).

The metamorphogenic type is also represented by one deposit in Kazakhstan, where diamonds are found in biotite gneisses, biotite-quartz, garnet-pyroxene and pyroxene-carbonate rocks. According to the reserves and the content of diamonds, it is ten times higher than the largest high-diamond-bearing kimberlite pipes. Diamonds have an extremely small crystal size, and jewelry and high-quality technical varieties have not yet been found.

Advertisements

Types of placer deposits of diamonds

Alluvial placers (river valleys) are leading in the scale of diamond mining from placers. Large deposits are rare and are usually formed by erosion of several indigenous sources or intermediate reservoirs of the surface type. Alluvial placers have a two-member structure: the upper floodplain facies of alluvium is represented by very weakly diamond-bearing gravel-sandy-argillaceous and silty sediments (“peat”), the lower channel facies is composed of productive rough-grained pebbles (“sand”).

Placers of the deluvial-proluvial type are formed on the slopes and in the logs near the indigenous sources and are small and medium in scale.

Coastal-marine placers are subdivided into underwater, beach and coastal terraces. The zone of such placers in southwest Africa extends for many hundreds of kilometers with a width of 5 to 20 km.

Placers of other industrial types do not play an important role in diamond mining.

Alluvial deposits of various types are subdivided into shallow and deep-lying deposits in depth. By the degree of remoteness from the source of the source are allocated placers near and far; The former are formed near the root source, the latter – at a distance of tens of kilometers in favorable geological and structural conditions.

Industrial types of graphite deposits.

Graphite was formed from organic compounds as a result of metamorphism of sedimentary rocks.

Among the graphite deposits, four groups of industrial deposit types are distinguished according to the geological conditions of their occurrence.

According to the size of the deposit, graphite deposits are subdivided (million tons) into: large ones – more than 1, medium ones – 0.5-1, small ones – up to 0.5.

The most widespread and the largest in its reserves are deposits of the Taygin, Madagascar, Noginsk, Mexican types.

Graphite deposits of the Ceylon and Botogul types are less common, less often they have large reserves, but they are distinguished by a high content of graphite in the ore and more valuable qualities.

General characteristics of graphite

Graphite is a gray-black crystalline substance with a metallic luster, greasy to the touch, harder than paper.

The structure of graphite is layered, within the layer the atoms are bound by mixed ion-covalent bonds, and between the layers – by essentially metallic bonds.

The carbon atoms in graphite crystals are in sp2-hybridization. The angles between the directions of the bonds are 120 *. As a result, a grid is formed, consisting of regular hexagons.

When heated without air access, graphite does not undergo any change to 3700 * C. At this temperature, it is expelled without melting.

Crystals of graphite are, as a rule, thin plates.

Due to the low hardness and very perfect cleavage, graphite easily leaves a trace on paper, greasy to the touch. These properties of graphite are due to weak bonds between atomic layers. Strength characteristics of these bonds characterize the low specific heat of graphite and its high melting point. Due to this, graphite has an extremely high refractoriness. In addition, it conducts electricity and heat well, is resistant to many acids and other chemical reagents, mixes easily with other substances, has a low coefficient of friction, high lubricity and cover ability. All this led to a unique combination of important properties in one mineral. Therefore, graphite is widely used in industry.

The carbon content of the mineral aggregate and the structure of graphite are the main attributes that determine the quality. Graphite is often called a material, which, as a rule, is not only monocrystalline, but also monomineral. In general, the aggregate forms of graphite matter, graphite and graphite-bearing rocks and enrichment products are meant. In them, besides graphite, there are always impurities (silicates, quartz, pyrite, etc.). The properties of such graphite materials depend not only on the content of graphite carbon, but also on the size, shape and mutual ratios of graphite crystals. From texture-structural features of the material used. Therefore, in order to evaluate the properties of graphite materials, it is necessary to take into account both the features of the crystalline structure of graphite and the texture-structural features of their other constituents.

General characteristic of diamond

Once people who hunted for diamonds, and did not suspect that the object of their passion is crystalline carbon, which forms soot, soot and coal. This was first proved by Lavoisier. He put the experience of burning a diamond, using an incendiary machine specially built for this purpose. It turned out that the diamond burns in air at a temperature of about 850-1000 * C, leaving no solid residue, like ordinary coal, and burns at a temperature of 720-800 * C in a jet of pure oxygen. When heated to 2000-3000 * C without access to oxygen, it passes into graphite (this is explained by the fact that the homopolar bonds between the carbon atoms in the diamond are very strong, which causes a very high melting point.

Diamond – a colorless, transparent crystalline substance, extremely refracting rays of light.
The carbon atoms in the diamond are in a state of sp3-hybridization. In the excited state, valence electrons are vaporized in carbon atoms and four unpaired electrons are formed.
Each carbon atom in a diamond is surrounded by four others, located away from it in the direction from the center at the tops of the tetrahedron.
The distance between atoms in tetrahedra is 0.154 nm.
The strength of all bonds is the same.
The whole crystal is a single three-dimensional skeleton.

At 20C, the density of the diamond is 3.1515 g / cm. This explains its exceptional hardness, which on the edges is different and decreases in sequence: octahedron – rhombododecahedron – cube. At the same time, the diamond has perfect cleavage (in the octahedron), and its flexural and compressive strength is lower than that of other materials, so the diamond is brittle, it breaks with a sharp impact and turns into powder when it is crushed. The diamond has maximum rigidity. The combination of these two properties makes it possible to use it for abrasive and other tools operating at a significant specific pressure.

The refractive index (2.42) and dispersion (0.063) of diamond are much higher than those of other transparent minerals, which, combined with maximum hardness, determines its quality as a precious stone.

Diamonds contain impurities of nitrogen, oxygen, sodium, magnesium, aluminum, silicon, iron, copper and others, usually in thousandths of a percent.

The diamond is extremely resistant to acids and alkalis, it is not wetted by water, but has the ability to adhere to some fatty mixtures.

Diamonds in nature occur both in the form of well-defined individual crystals and polycrystalline aggregates. Correctly formed crystals have the form of polyhedra with planar faces: octahedron, rhombododecahedron, cube and combinations of these forms. Very often on the faces of diamonds there are numerous stages of growth and dissolution; If they are indistinguishable to the eye, the faces appear curved, spherical, in the form of an octahedroid, hexahedroid, cuboid and their combinations. The different shape of the crystals is due to their internal structure, the presence and nature of the distribution of defects, and also the physicochemical interaction with the surrounding medium.

Among the polycrystalline formations, ballas, carbonado, and beads are distinguished.

Ballas are spherulite formations with radial-radiant structure. Carbonado – cryptocrystalline aggregates with the size of individual crystals of 0.5-50 microns. Board – clear aggregates. Ballas and especially carbonado have the highest hardness from all types of diamonds.

Active and passive technologies of solar energy

More than half a century, scientists have tried a huge number of different options and ways to extract and use solar energy. Expensive and inefficient technologies gave way to attractive and inexpensive developments that do not stop improving over the years. Let’s highlight the most common technology groups of the “solar” industry and try to identify the most attractive options for the consumer. First, it is necessary to determine the classification of “solar” technologies, separated by scientists into 4 groups: active, passive, direct (or “direct”) and indirect (indirect).

Active – together with the transducers mechanisms are involved, electric motors, pumps. Solar energy is used for heating water, lighting, ventilation.

Passive – differ from active by the absence in the contours of systems of any mechanisms, moving parts. A special feature of constructing passive solar structures for the organization of ventilation and heating systems is the selection of appropriate building materials for physical parameters, a specific layout of the room, and the placement of windows.

Direct or “direct” technologies include systems that convert solar energy in the course of one level or stage.
To the group of “indirect” technologies belong systems whose process of functioning includes multilevel transformations and transformations to obtain the required form of energy.

Based on the above classification of groups of solar energy technologies, it is possible to easily characterize the spheres of human activity, where the energy of the sun has become most widespread.

Advantages and disadvantages of solar energy

Advantages
1. The general availability and inexhaustibility of the source.
2. Theoretically, complete safety for the environment, although there is a possibility that the widespread introduction of solar energy can change the albedo of the earth’s surface and lead to climate change (however, with the current level of energy consumption, this is highly unlikely).

Disadvantages
1. Dependence on weather and time of day.
2. As a consequence, the need for energy storage.
3. High cost of construction.
4. The need for constant cleaning of the reflecting surface from dust.
5. Heating of the atmosphere above the power plant.

Is solar energy from the technical and economic point of view ideal? Unfortunately, not really. We will try to highlight the main advantages and disadvantages of this method of extracting energy.

Let’s start with the positive sides. First, “raw materials”, i.e. Sunlight, will never end. The second plus of solar energy is its general availability, as the sun shines in the south and west, in Africa and Europe.
The issue of absolute safety of these technologies for the environment is contradictory. Of course, this is not nuclear energy and not the extraction of oil and gas, but at this stage of development of “solar” technologies, harmful substances are used in the manufacture of batteries, which in one way or another can harm nature. Ready-made samples (photocells) contain poisonous substances, such as lead, cadmium, gallium, arsenic.

As for the service life of the converters (30-50 years), the problem arises here for the subsequent processing of obsolete modules, and the solution of the problem of their utilization has not yet been found. The obvious shortcoming of the process of extracting energy is the so-called impermanence. Solar systems are not able to work at night, and in the evening and in the early twilight the efficiency of stations falls several times.

Severe influence is exerted by weather factors. Many complain about the relative high cost of solar cells, inadequate efficiency in terms of material costs and payback (at the moment). The problem of technical support and maintenance is the “underwater stone” of the functioning of modern “solar farms”. The developers argue that the intense heating of photocells significantly reduces the efficiency of the system as a whole, so here it is necessary to provide a solution to the problem of cooling modules. Also, solar panels must be periodically cleaned from dust and dirt, and in the case of working with an installation area of ​​several square kilometers with cleaning, considerable difficulties can arise.

Ideal, at first glance, energy production technology even today there are a number of shortcomings, but you can be sure that this is just an indicator of improving solar energy. Every day of technological progress can eradicate one flaw after another, so it’s a matter of time.

What is a solar collector?

These devices today are the most common type of solar converters. The device operates at a temperature of from one hundred to two hundred degrees.

Talking about the application of these settings can be endless.

Already in our days, solar collectors perform a huge range of work. With the help of collectors, they heat food, save salt, extract water from wells.

Through concentrated solar energy, you can dry vegetables or fruits, and also freeze food.

It should be said that the main advantage of using a thermal solar converter is to provide a high efficiency.
Thus, recent developments allow us to speak about forty-five and even sixty percent. By the way, the level of efficiency of thermal solar receivers can be increased by supplementing them with special mirror surfaces.

The main function of such a surface is to concentrate the incoming radiation. If we consider these devices as a means of providing energy to an apartment house, then the most practical promises are so-called focons.

These are flat solar cells with linear concentrators. This device is represented in the form of a V-shape. By the way, the device can be not only flat, but also paraboloid.

Of course, such an improved design will cost the consumer much more expensive, but the effect will be appropriate.

For household needs, the collector, which performs the role of a water heater, is perfect. The structure includes a box with a coil, a tank with cold water, a tank-battery and pipes.

The main thing is to install the box correctly. It should be at an angle of 30-50 degrees and be directed to the south. Cold water is at the bottom of the box, it is heated and replaced by incoming cold water, enters the storage tank.

The plant’s capacity during the day is about two kilowatt-hours per square meter. Water can be heated to sixty or seventy degrees, which allows it to be used for a variety of purposes (heating, shower, etc.).

Also, the device boasts a high efficiency. Usually it reaches forty percent. The principle of solar collectors in many ways resembles the principle of greenhouses. Such collectors can be made of different materials – wood, metal, plastic.

On the one hand they are closed with a single or double glass. To ensure complete absorption of sunlight, a sheet of metal is inserted into the box. As a rule, this sheet is painted in black.

The box contains air or water that is heated and then fed into the tank by the action of a fan or pump.