Minerals definition classification. Minerals and mineralogy
The classification of minerals by chemical composition is based on the chemical composition and crystal structure
Since each mineral is a specific chemical compound with a characteristic structure, the modern classification of minerals is based on the chemical composition and crystal structure. There are ten classes of minerals: silicates, carbonates, oxides, hydroxides, sulfides, sulfates, halides, phosphates, tungstates.
and molybdates, native elements.
The ratios between the quantities of mineral species by class and their content in the earth's crust are given in table -1. As can be seen from this table, the most common are silicates and aluminosilicates, as well as oxides and carbonates, which make up almost 94% of the earth's crust, which corresponds to the total abundance of chemical elements in nature (see table-2. Systematics of all chemical elements of the earth's crust according to their quantitative role in the composition of minerals was carried out by A.S. Cookery (see table-3).
For the most common minerals of the silicate class in nature, classification according to structural features is widely used: island - olives, garnet, sillimanite, melinite; ring -beryl; chain-pyroxenes; tape-amphiboles, hornblende; sheet micas, chlorites, framework feldspars, feldspathoids. Characteristics of the main rock-forming minerals are given below.
Table 1. Distribution of mineral species between individual classes of minerals and their content in the earth's crust
silicates. The most numerous and widespread class of minerals. The silicates are characterized by a complex chemical composition
and isomorphic substitutions of some elements and complexes of elements by others. Common to all silicates is the presence in the anionic group
silicon-oxygen tetrahedra 4- in various combinations. The total number of mineral types of silicates is about 800. In terms of abundance, silicates account for more than 75% of all minerals in the lithosphere.
Silicates are the most important rock-forming minerals that make up the bulk of rocks (feldspars, micas, hornblende, pyroxenes, olivine, chlorite, clay minerals). The most common in nature are minerals of the feldspar group.
2. Carbonates. Carbonates are salts of carbonic acid. This is a large group of minerals, many of which are widely distributed. They are most widely distributed on the earth's surface and in the upper part of the earth's crust. Carbonates are found mainly in sedimentary and metamorphic (marble) rocks. Most carbonates are anhydrous and are simple connections, mainly Ca, Mg and Fe with complex anion 2-. Characteristic representatives of the class of carbonates are calcite, dolomite, malachite, siderite, magnesite.
3-4. Oxides and hydroxides. Oxides are compounds of elements with oxygen; hydroxides also contain water. In the earth's crust, oxides and hydroxides account for about 17%. The most common minerals of this class are the oxides of Si, Al, Fe, Mn, Ti, while the mineral quartz SiO2 is the most common mineral on earth (about 12%). In the crystal structures of minerals of the class of oxides, metal cations are surrounded by oxygen anions O2- (in oxides) or hydroxyl [OH] 1- (in hydroxides). Characteristic representatives: quartz, corundum, magnetite, hematite oxides; limonite, bauxite - hydroxides.
Table 2. Average abundance for the first ten chemical elements in the earth's crust, % by mass and their mineral productivity.
Table-3. The average composition of the Earth and the earth's crust,% by weight (according to Beus A.A., 1972)
5. Sulfides. There are more than 200 types of sulfur and similar minerals, but their total content in the earth's crust is not high, about 1%. From a chemical point of view, they are derivatives of hydrogen sulfide H2S. The origin of sulfides is mainly hydrothermal, as well as magmatic, rarely exogenous. Minerals of the sulfide class are formed, as a rule, at a depth below the boundary of the penetration of atmospheric oxygen into the earth's crust.
Once in the near-surface region, sulfides are destroyed, in addition, reacting with water and oxygen, they form sulfuric acid, which acts aggressively on rocks. Thus, sulfides are a harmful impurity in natural building materials. The most common are iron sulfides - pyrite, chalcopyrite; other representatives
-galena, sphalerite, cinnabar.
6. Sulfates. Sulphates are salts of sulfuric acid. Many of them are soluble in water, since they are sediments from marine or lacustrine salt water bodies. Some sulfates are products of the oxidation zone; sulfates are also known as products of volcanic activity. Sulfates account for 0.5% of the mass of the earth's crust. There are anhydrous and aqueous sulfates, containing, in addition to the anionic complex 2- common to all, also additional anions (OH) 1-. Representatives: barite, anhydrite - anhydrous, gypsum, mirabilite - water.
7. Halides. This class includes fluorine, chloride and very rare bromine and iodine compounds. Fluorine compounds, for the most part, are associated with magmatic activity, they are sublimates of volcanoes or products of hydrothermal processes, sometimes they are of sedimentary origin. Chloride compounds Na, K and Mg are predominantly chemical sediments of seas and lakes and the main minerals of salt deposits. Halides make up about 0.5% of the mass of the earth's crust. Typical representatives: fluorite (fluorspar), halite (rock salt), sylvin, carnallite.
8. Phosphates. Minerals of this class are salts of phosphoric acid; the crystal structure of these minerals is characterized by the presence of anionic complexes [PO4]3-. These are mainly rare minerals; The most widely distributed mineral-magmatic origin is apatite and sedimentary biogenic phosphorites having the same chemical composition.
9. Tungstates and molybdates. This class contains a small number of mineral species; the composition of minerals corresponds to salts
33 tungstic and molybdic acids. The main representatives are wolframite and scheelite.
10. Native elements. About 40 chemical elements are known in the native state in nature, but most of them are very rare; in general, native elements make up about 0.1% of the mass of the earth's crust. In the native state, metals are found - Au, Ag, Cu, Pt, Sn, Hg; semimetals - As, Sb, Bi and non-metals - S, C (diamond and graphite).
WE RECOMMEND reposting the article on social networks!Every person at least once in his life saw minerals - products of natural chemical reactions that took place within the earth's crust millions of years ago. At the same time, not everyone can tell about what a mineral is and why it is needed. Our article will go into detail about the types of mineral deposits, as well as how to use them.
What is a mineral?
Minerals are solid inorganic substances of natural origin. They have a crystalline structure, which is their main distinctive feature. Some minerals can be produced artificially. Regardless of the origin, they will have a number of useful properties.
Are there liquid minerals? If we take the usual conditions of life, then yes. This, for example, is natural mercury - a native substance that has hardness only at low temperatures. Scientists also classify some types of ice as minerals. However, water is not included in the group under consideration.
The question of what a mineral is has not been fully resolved to this day. So, a few experts attribute oil, bitumen and asphalt to the group of mineral substances. The validity of such claims is questionable.
Types of minerals
According to Bauer and Fersman, chemists late XIX centuries, all mineral rocks are divided into gems, organogenic stones and non-ferrous substances. Such a classification has such a peculiar appearance due to the deep conviction of pragmatic academicians that all stones and minerals are intended for the manufacture of various products - tools and jewelry.
In order to better understand the question of what minerals are, it is worth bringing the most common scientific classification. According to the structural-chemical principle, minerals are divided into rock-forming - making up the majority of rocks, as well as rare, ore and accessory (not constituting more than 5% of the rock).
The native class of minerals includes metals and metalloids. Ore substances form the bulk of the native group. Accessory minerals are characterized by a special rarity.
Chemical classification
The chemical structure of most minerals is approximately the same. At present, the division of the considered substances into classes is accepted. This results in the following classification:
- silicates. Numerous class, including more than 800 different mineral deposits. Silicates make up the majority of metamorphic and igneous rocks. Some minerals here are distinguished by a common structure and composition. As an example, it is worth highlighting pyroxenes, micas, feldspars, amphiboles, clay materials and much more. The composition of most silicates is referred to as aluminosilicate.
- Carbonates. This class includes about 80 mineral rocks. Dolomites, calcites and magnets are common here. The origin is due to individual aqueous solutions. Destroyed in acids.
- Halides are a group of one hundred different minerals. They are readily soluble, formed from sedimentary rocks. The most common substance is halite.
- Sulfides are minerals that are destroyed in the weathering zone. A typical representative is pyrite.
- sulfates. They have a light color and a low level of hardness. Gypsum is the most widely used.
- oxides and hydroxides. They make up about 17% of the mass of the earth's crust. The main types are opals, limonites and quartz.
Thus, almost all minerals have similar features, although the composition of the substances is different.
Variety of minerals
What is a mineral? It is not easy to answer this question. It should be taken into account that in today's world there are more than 4 thousand different types of underground wealth. Minerals open and "close" annually. For example, a substance found in rocks by its very existence proves the inconsistency of the whole classification compiled by scientists. Such cases are far from uncommon.
A photo of silicates is presented to your attention below.
It should be borne in mind that 4 thousand minerals is not such a big figure. If we compare it with the total number of inorganic compounds, then the difference will be obvious: the latter contain about a million species. How do geologists explain such a poor variety of mineral wealth? First, the prevalence of elements in solar system. Our planet is dominated by silicon and oxygen. The combination of these substances leads to the appearance of silicates - the overwhelming mineral group on Earth. On the other hand, the minerals are so scattered that the search for new elements will be the work of several hundred more generations. The second reason for the limited nature of minerals is the instability of most chemical compounds.
Origin of minerals
Scientists name three main ways of origin of mountain minerals. The first option is called endogenous. Underground hot alloys, which are commonly called magmatic matter, are introduced into the earth's crust, and then solidify there. Magma itself is formed as a result of volcanic eruptions. It goes through three stages: from a hot state, magma becomes solid - this is the result of pegmatite processes. After that, she finally freezes. This is a consequence of postmagmatic processes.
There is also an exogenous version of the origin of minerals. In this case, physical and chemical decomposition of substances occurs. At the same time, new formations are formed that are highly compliant to the environment. A simple example: as a result of weathering of endogenous material, crystals are formed.
The last way of origin of minerals is metamorphic. All substances will change under the influence of certain conditions - regardless of the options for the formation of rocks. In fact, the original sample is changing - it acquires new properties and composition elements.
Properties of minerals
The most important property of any mineral formation is the presence of a crystal-chemical structure. All other features of the considered breeds follow precisely from this.
To date, a unified classification of diagnostic features characteristic of mineral substances has been developed. Here it is necessary to highlight the hardness, determined on the Mohs scale, as well as color, gloss, fracture, cleavage, magnetism, brittleness and tint. Each property of the rocks under consideration will be studied in detail below.
The concept of hardness
What is hardness? There are several definitions for this concept. The most common description characterizes hardness as the level of resistance of a certain body to scratching, squeezing or cutting. The hardness level is determined on the Moss scale. It contains special rocks, each of which is characterized by the ability to scratch surfaces with a sharp end. Moss made the top ten of the most common elements. The softest material here is talc and gypsum. As you know, gypsum, getting into the water, increases in size up to 30%. The hardest type and rock of the mineral is diamond.
Carrying the substance over the glass should leave behind scratches of various depths. The very fact of the existence of a scratch already assigns to the mineral at least the fifth class out of ten. Most solids found in groups of minerals with non-metallic luster. It is the shine that is the second important property minerals, and it is directly related to hardness.
Shine
The level of brilliance of metals is checked by reflecting the rays of the sun from them. There are two levels of gloss - metallic and non-metallic. The first group includes rocks that give a black line when carved on glass. Such substances are opaque even in very thin fragments. Types of underground minerals with non-metallic luster include graphite, magnetite, coal and some other substances. All of them are poorly reflected in the sun and give a dark line. A small part of materials with a metallic sheen are substances that give a color line: green (gold), red (copper), white (silver), etc.
Minerals with a metallic sheen reflect sunlight better. By themselves, they have a high hardness. Ore occupies a special place here.
Color
Color, unlike hardness and luster, is not a constant feature for most minerals. Thus, the hardness or luster remains unchanged over time. The color changes depending on storage conditions. Examples of minerals that rarely change color are malachite, which never changes its green color, and gold, which always remains yellow.
You can see a photo of malachite below.
The color also changes depending on the state of the mineral. For example, in geology, the concept of line color is common. A mineral that scratches a glass surface leaves behind a small amount of powder, which forms a line. The color of such a powder often differs from the natural color of the stone. It's all about the composition of the mineral: it may include calcite, which changes color depending on the amount and method of mixing with other substances.
Fracture and cleavage
Cleavage refers to the property of a mineral to split or split in a certain direction. So, after a break, a smooth shiny surface is most often formed. To achieve this result, you need to split the mineral along a strictly defined line. There are five gradations of cleavage:
A diagnostic feature for many minerals is the presence of several cleavage directions at once. As a result of splitting, the mineral has kinks, which also has certain properties. So, scientists distinguish five types of fracture:
- conchoidal - similar to a shell;
- splintery - fracture is characterized by fibrous or fibrous materials;
- uneven - the presence of imperfect cleavage (for example, in apatite);
- stepped - according to the results of cleavage, an almost perfectly smooth surface is formed (in places it may, however, have irregularities in the form of steps);
- smooth - according to the results of soldering, there are no noticeable bends or irregularities on the surface of the mineral.
There are a number of other signs by which minerals can be identified. This, for example, tarnish - the presence of a thin colored film formed on the substance as a result of weathering or oxidation. It is also necessary to highlight fragility, indicating the strength of the mineral, and magnetism, characterized by the content of ferrous iron.
Minerals in industry
In what areas social activities minerals used? These are construction, metallurgy, as well as chemical production.
Building materials are often diluted with certain minerals, which allows you to adjust the strength and quality of the substance. In the chemical industry, the presence of the elements in question is also not uncommon. Mineral components are used in cosmetic, medical and food fields. For example, in pharmacies there are many drugs that include vitamins and minerals. These two components work well together and complement each other. They help improve people's health and improve their appearance.
The extraction and study of minerals have always been considered important and relevant activities. It is necessary to fully support the conduct of scientific research in the field of geology, as well as the active use of vitamins and minerals in everyday life.
The classification of minerals is based on the chemical composition:
1. Native elements: sulfur, graphite.
2. Sulfides: pyrite.
3. Oxides and hydroxides: quartz, opal, limonite.
4. Carbonates: calcite, dolomite, magnesite;
5. Sulphates: gypsum, anhydrite;
6. Halides: halite;
7. Silicates: olivine, pyroxenes (augite), amphiboles (hornblende), kaolinite, micas (muscovite, biotite), feldspars (albite, orthoclase, microcline, labrador).
Each mineral has its own physical properties. Most minerals have a crystalline structure, ᴛ.ᴇ. their constituent elements are located in space in a strictly ordered manner, forming a crystal lattice.
Amorphous minerals, unlike crystalline ones, do not have a regular internal structure (opal, amorphous magnesite), they are a homogeneous mass, similar to plasticine, bone.
The study of minerals can be carried out by the macroscopic method. For a more accurate study, microscopic examinations are used.
The macroscopic method is based on the study of the external features of minerals. These features include the morphological appearance and physical properties of minerals.
Appearance of minerals:
1. Sometimes minerals are found in the form of single regular polyhedra. They are called crystals (quartz, gypsum, calcite).
2. Families of crystals intergrown with bases form druses and brushes (calcite, quartz).
3. Most often, its minerals are found in the form of granular aggregates, the mass of which consists of small grains of irregular shape.
4. If the grains have a certain geometric shape, then the following are formed: a) needle-like, columnar, prismatic; grains elongated in one direction (hornblende); b) lamellar, leafy - elongated in two directions (mica, gypsum).
5. Concretions - spherical intergrowths of grains with a shellish or radially radiant structure.
6. Geodes - accumulation of grains on the walls of voids in rocks. The growth of minerals occurs from the walls to the center of the void.
Physical properties of minerals
Studying physical properties allows you to recognize minerals. The most characteristic properties for each mineral are called diagnostic.
The color of minerals is very diverse. Some minerals come in different colors (quartz - milky, water-transparent, smoky). For other minerals, color is a permanent property and can serve as a diagnostic (sulfur is yellow). There are minerals that change their color based on the light. For example, a Labrador when turning in the light shines blue, green. This property is called iridescence.
The color of the line is ϶ᴛᴏ the color of the mineral in powder. Some minerals have a different color in powder than in a piece (pyrite is straw yellow, the line is brownish black).
Luster should be metallic (pyrite), semi-metallic (luster of tarnished metal - graphite) and non-metallic (glassy, bold mother-of-pearl, matte - quartz, sulfur, mica, kaolin).
Cleavage - the ability of minerals to split in certain directions with the formation of smooth polished planes. There is a very perfect cleavage - the mineral is easily split into leaves (mica); perfect cleavage - the mineral breaks with a weak hammer blow into regular geometric shapes (calcite); medium cleavage - when split, planes are formed, both even and uneven surfaces (feldspars); imperfect cleavage - cleavage planes are practically not detected (quartz, sulfur). The fracture of minerals with imperfect cleavage is always either uneven or conchoidal (quartz).
Hardness - ϶ᴛᴏ the degree of resistance of a mineral to external mechanical influences. To determine the hardness, the Mohs scale was adopted, which uses minerals with a known and constant hardness (Table 1).
Mohs hardness scale
Table 1 -
The sequence of actions in determining the hardness of minerals: a mineral is drawn on glass (tv. 5). If a scratch remains on the glass, then the hardness of the mineral is equal to or greater than 5. Then reference minerals with a hardness greater than 5 are used. For example, if the tested mineral leaves a scratch on the reference with a hardness of 6, and when scratched its quartz produces a deep scratch, its hardness is 6.5.
It is worth saying that some minerals are characterized by special, only inherent properties. So carbonates react with hydrochloric acid (calcite boils in a piece, dolomite in powder, magnesite in hot acid).
Halides have a characteristic taste (halite - salty).
Minerals are characterized by varying resistance to weathering. Some minerals are destroyed physically, forming fragments, other minerals undergo chemical transformations, being converted into other compounds (table 2).
Resistance of minerals to weathering
table 2
| Group according to the degree of stability | Name of minerals | The nature of the changes |
| The most stable, insoluble | Quartz Muscovite Limonite | Physical grinding without changing the chemical composition |
| Medium resistant, insoluble | Orthoclase Albite Augit Hornblende | Physical destruction and hydrolysis: secondary minerals are formed: kaolinite, limonite, opal |
| Less stable, insoluble | Labrador Biotite | The same, but the process is more intense |
| Weakly stable, insoluble | Pyrite Olivine | Oxidation: limonite and sulfuric acid are formed Oxidation: serpentine, chlorite, magnesite are formed |
| slightly soluble | Dolomite Calcite | Physical disintegration and dissolution |
| Medium soluble | Anhydrite Gypsum | Dissolution, hydration, dehydration |
| highly soluble | Halite | Intensive dissolution, plastic flow with prolonged action of one-sided exposure |
Method for the determination of minerals.
It is extremely important to use the mineral guide for practical work.
Work sequence:
1. Determine the appearance of the grains of the mineral aggregate.
2. Determine the color of the mineral, if the mineral is dark in color, then run the mineral over a porcelain plate to determine the color of the line (powder).
3. Determine the brilliance of the mineral.
4. To determine the hardness range, run the mineral over the glass.
5. Minerals of medium hardness (3-3.5) should be checked for reaction with
10% hydrochloric acid solution.
6. Try to find smooth polished edges on the sample - ᴛ.ᴇ. determine cleavage.
7. Based on the set of features in the guide, find the name and composition of the mineral.
8. Mark the composition of which rocks this mineral is included.
Enter data on minerals in Table 3.
Characteristics of rock-forming minerals
Table 3
List of minerals to study:
1. Native elements: graphite, sulfur.
2. Sulfides: pyrite.
3. Oxides and hydroxides: quartz, chalcedony, opal, limonite.
4. Halides: halite, sylvin.
5. Carbonates: calcite, dolomite, magnesite.
6. Sulphates: gypsum, anhydrite.
7. Silicates: olivine, garnet, augite, hornblende, talc, serpentine, kaolin, micas, chlorite, orthoclase, microcline, albite, nepheline.
Control questions
1. What are minerals?
2. What minerals are called rock-forming?
3. In what form are minerals found?
4. For which minerals is color diagnostic?
5. What is the color of the line, examples.
6. What is the brilliance of minerals?
7. How is the hardness of minerals determined?
8. What is cleavage?
9. What minerals can be dissolved in water?
10. Which minerals swell?
11. What is hydration and dehydration?
12. Which minerals are the most resistant to weathering?
BIBLIOGRAPHY
Pavlinov V.N. and etc.
Hosted on ref.rf
geology. – M.: Nedra, 1988. p. 5-7, 11-49.
LAB #2
STUDY OF IAGMATIC ROCKS
The purpose of the work: to acquire skills in the definition of igneous rocks. To study the engineering and construction characteristics of igneous rocks and their application in construction.
Equipment: educational collection of igneous rocks, magnifiers,
Mohs scale.
General information about rocks.
Rocks are called independent geological bodies, consisting of one or more minerals of more or less constant composition and structure.
According to the method and conditions of formation, all rocks are divided into igneous, sedimentary and metamorphic.
The mineralogical composition of rocks is different. Οʜᴎ may consist of one (monomineral) or several minerals (polymineral).
The internal structure of rocks is characterized by their structure and texture.
Structure - ϶ᴛᴏ the structure of the rock, due to the shape, size and relationship of its constituent parts.
The texture of the rock determines the distribution of its constituent parts in space.
All rocks are classified according to the conditions of formation into igneous, sedimentary and metamorphic rocks.
Conditions for the formation of igneous rocks.
Igneous rocks are formed as a result of the cooling of magma. Magma - ϶ᴛᴏ stone melt of silicate composition, formed on great depths in the bowels of the earth. Magma can cool deep in the earth's crust under the cover of outcropping rocks and on or near the surface of the earth. In the first case, the cooling process proceeds slowly, and all the magma has time to crystallize. The structures of such deep rocks are fully crystalline and granular.
With the rapid rise of magma to the surface of the earth, its temperature drops rapidly, gases and water vapor are separated from the magma. In this case, the rocks are either not completely crystallized (glassy structure) or partially crystallized (semicrystalline structure).
Deep rocks are called intrusive. Their structures are: fine-grained (grains<0,5 мм), среднезернистая (размер зерен 0,5-1 мм), крупнозернистая (от 1 до 5 мм), гигантозернистая (>5 mm), uneven-grained (porphyritic).
Erupted rocks are called effusive. Their structures are porphyritic (separate large crystals stand out in the cryptocrystalline mass), aphanitic (dense cryptogranular mass), glassy (the rock almost entirely consists of a non-crystallized mass - glass).
Igneous Rock Textures: Intrusive rocks are almost always massive. In effusive rocks, along with a massive texture, there are porous and vesicular ones.
The physicochemical conditions of rock formation at depth and on the surface are sharply different. For this reason, different rocks are formed from magma of the same composition under deep and surface conditions. Each intrusive rock corresponds to a certain outflowing rock.
Along with the classification of igneous rocks according to the conditions of occurrence, they are classified according to their chemical composition based on the content of silicic acid SiO 2 (Table 4).
Classification of igneous rocks.
Table 4
| Breed composition | Rocks are intrusive (deep) | Effusive rocks (poured out) | |
| chemical | mineralogical | ||
| Acidic SiO 2 > 65% | Quartz, feldspar, mica | Granite | Liparite, pumice, quartz porphyry, obsidian |
| Medium SiO 2 (65-52%) | Potassium feldspar, plagioclase, hornblende Plagioclase, hornblende | Syenite Diorite | Trachyte, orthophyre Andesite, andesite porphyrite |
| Basic SiO 2 = 52-40% | Plagioclase, pyroxene Plagioclase | Gabbro Labradorite | Basalt, diabase |
| Ultrabasic SiO 2< 40 % | Olivine Olivine, pyroxene Pyroxene | Dunite Peridotite Pyroxenite |
Engineering and construction characteristics of igneous rocks.
All igneous rocks have high strength, significantly exceeding the loads possible in engineering and construction practice, are insoluble in water and practically impermeable (except for fractured varieties). Due to this, they are widely used as foundations for critical structures (dams). Complications during construction on igneous rocks arise if they are fractured and weathered: this leads to a decrease in density, an increase in water permeability, which significantly worsens their engineering and construction properties.
Application in construction.
Intrusive igneous rocks such as granite, syenite, diorite, gabbro, labradorite are used as facing material.
Basalts and diabases are used for stone casting as paving stones for paving streets, mineral wool.
Ultrabasic rocks are used as refractory raw materials. Pumice is used as a polishing and abrasive material. Obsidian is used as an ornamental stone. Igneous rocks are widely used as rubble and crushed stone.
Method for determination of igneous rocks.
When establishing the type of igneous rock, it is extremely important to first of all find out whether it belongs to intrusive or effusive. Intrusive rocks have a full-crystalline structure - minerals are visible to the naked eye, and the entire rock mass is an aggregate of crystalline grains. In effusive rocks, only part of the substance (porphyritic phenocrysts) has acquired a crystalline structure, while the rest of the mass consists of a substance whose granular structure is indistinguishable.
The next stage is the determination of the mineral composition. Acid and medium rocks are colored in gray tones, basic and ultrabasic rocks are dark and black. Quartz is found in significant amounts only in acidic rocks. Syenites and diorites are devoid of quartz, diorite contains up to 30% hornblende.
Liparites, trachytes and andesites differ in phenocryst minerals: in trachytes they are represented by potassium feldspar, in andesites by plagioclase and hornblende, in liparites by quartz and feldspar.
Gabbro and ultramafic rocks are dark in color. In gabbro, light grains are represented by plagioclase; ultramafic rocks consist only of dark-colored minerals.
Determine the external signs of igneous rocks in the educational collection and describe them in a notebook according to the plan:
1. Name of the breed.
2. Group according to the content of SiO 2 .
3. Group according to the method of education.
4. Structure.
5. Texture.
7. Mineral composition.
Control questions.
1. What is commonly called a rock?
2. How are rocks classified?
3. What is the structure?
4. What structures are characteristic of igneous rocks?
5. What is texture?
6. What textures are typical for igneous rocks?
7. How are igneous rocks formed?
8. What is the difference between intrusive and effusive rocks?
9. How are igneous rocks classified according to the content of SiO 2?
10. Name the erupted analogues of granites, syenites, diorites, gabbro.
11. What are the engineering and geological properties of igneous rocks?
12. How are igneous rocks used in construction?
BIBLIOGRAPHY
Pavlinov V.N. and etc.
Hosted on ref.rf
Manual for laboratory classes in general
geology.-M.: Nedra, 1988. p. 50-64.
LAB #3
STUDY OF SEDIMENTARY ROCKS
The purpose of the work: to acquire skills in the determination of sedimentary rocks. To study the engineering and construction characteristics of sedimentary rocks. To study the use of sedimentary rocks in construction.
Equipment: educational collection of sedimentary rocks,
solution of 10% hydrochloric acid, magnifying glass.
Conditions for the formation of sedimentary rocks
Sedimentary rocks are formed in the surface zone of the earth's crust under conditions of low temperatures and pressures.
Weathering processes lead to the destruction of primary rocks. Destruction products are moved mainly by water flows and, being deposited, gradually form sedimentary rocks.
According to the method of formation of mineral matter, sedimentary rocks are divided into clastic, chemogenic and organogenic.
Clastic rocks are formed from fragments of destroyed rocks, most often they accumulate as marine sediments.
The classification of clastic rocks is based on: 1) the size of the clasts; 2) the degree of their roundness (rounded and non-rounded) and 3) the presence or absence of cement (loose and cemented) (table 5).
Classification of clastic rocks.
Table 5
| Breed group | Debris dimensions, mm | Loose rocks | cemented rocks | ||
| rounded | unrounded | rounded | unrounded | ||
| Coarse clastic (psephites) | > 200 200-10 10-2 | Boulders Pebbles Gravel | Blocks Rubble Grass | Boulder conglomerates Pebble conglomerates Gravel conglomerates | Blocky breccias Breccias |
| Sandy (psammites) | 2-1 1-0,5 0,5-0,25 0,25-0,1 | Sands Coarse-grained Coarse-grained Medium-grained Fine-grained | Sandstones Coarse-grained Coarse-grained Medium-grained Fine-grained | ||
| Silts | 0,1-0,01 | Silts (loesses, loams, sandy loams) | Siltstones | ||
| Pelites | < 0,01 | Clay | Argillites |
The structures of detrital rocks are detrital, differing in the shape and size of fragments (for example, coarse clastic, rounded). In clay rocks - pelitic.
Textures are often layered, loose.
Coarse clastic rocks and sands are widespread, characterized by high porosity and permeability, and are usually saturated with groundwater. Harmful impurities in the sands are iron oxides, gypsum, mica, clay particles. Under load, these rocks usually do not compact. During earthquakes, these rocks can liquefy.
The most stable minerals predominate in the sands: quartz, micas.
Clay rocks are characterized by high porosity (up to 90%), moisture, plasticity, stickiness, swelling, and shrinkage. With increasing humidity, their strength decreases sharply, they can go into a fluid state. Despite the high porosity, their water permeability is negligible, since the porosity is formed by closed micropores. Clays in their composition contain more than 30% clay particles (kaolinite). The rest is accounted for by dusty and sandy particles.
Loess breeds are among the very common breeds on the territory of Kazakhstan. These are polymineral rocks, consisting of silty particles of quartz, feldspars, calcite and micas. Characteristic features loess is their low water resistance, they quickly soak and erode, and are also capable of subsidence. It is expressed in the ability of loess to reduce its volume when moistened.
Siltstones and mudstones are formed during the "petrification" of sandy-silty and clayey rocks. These rocks are layered, easily weathered, sometimes soaked in water.
Chemogenic rocks are formed as a result of precipitation from aqueous solutions of chemical precipitation. This process occurs in a hot dry climate in drying up reservoirs. Οʜᴎ are classified by composition.
Carbonate rocks - dense limestones with a fine-grained structure consist of calcite, dolomites with a fine-grained structure consist of dolomite. Easily determined with HCl acid (limestone - in a piece, dolomite - in powder). The textures are massive.
Halide rocks are rock salt (salty) and sylvinite (bitter-salty). The structures are crystalline-granular, the textures are massive or layered.
sulfate rocks
Gypsum is a rock consisting of the mineral gypsum, light in color, fine-grained.
Anhydrite is a rock consisting of the mineral anhydrite, white-bluish in color, dense, fine-grained.
common feature chemogenic rocks is their solubility in water. Rock salt and sylvinite are easily soluble, gypsum, anhydrite are moderately soluble, limestone, dolomite are sparingly soluble.
Biochemogenic rocks are formed as a result of the accumulation and transformation of the remains of animals and plants, often with an admixture of inorganic material.
Carbonate rocks
Organogenic limestones consist of shells of calcite composition. If it is possible to determine the name of the organisms that make up the limestone, then the name of the rock is given by them. For example, coral limestone, shell limestone.
Chalk is a weakly cemented powder rock, consisting of calcite remains of planktonic algae.
Marls are a carbonate-argillaceous rock, light in color with conchoidal cleavage. Reacts with HCl, leaving a dirty spot on the rock surface.
Structures of organogenic rocks are organogenic; textures are dense and porous.
Siliceous rocks:
Diatomite is a light chalk-like rock. white color͵ consists of the remains of diatomaceous algae of opal composition.
Tripoli is a light, weakly cemented yellowish rock consisting of opal.
Opoka - gray, dark gray to black rock, porcelain-like. Also composed of opal.
Jasper is a dense and hard rock, composed of chalcedony - cryptocrystalline quartz. Beautifully colored (red, green, striped colors).
Engineering and construction properties of sedimentary rocks.
Rocks that are in the sphere of human activity are called soils.
Coarse-grained soils. The strength of these soils depends on the composition of the fragments and their packing. Soils consisting of fragments of igneous rocks have the greatest strength. The packaging of debris should be loose and dense. In different-grained soils, the packing is denser.
Sandy soils. The most dangerous varieties of sandy rocks are quicksand. These are water-saturated sands, which, when opened by pits, liquefy and set in motion.
Clay soils. Clay minerals, having a size< 0,001 мм, являются дисперсными частицами, ᴛ.ᴇ. для них характерен электрический заряд. По этой причине эти частицы притягивают к своей поверхности диполи воды. Вокруг каждой частицы образуется пленка воды, включающая два слоя: ближе к частице – прочно связанная вода, дальше – рыхлосвязанная.
The properties of clays are highly dependent on moisture content. If only tightly bound moisture is contained, then the clay will have the properties solid body, if loosely bound moisture is also contained, the clay becomes plastic and fluid.
Clays are characterized by special properties, such as swelling, shrinkage, water resistance, stickiness.
Cemented clastic rocks. Their strength depends on the composition of the cement. The most durable cement is siliceous, the weakest is clayey.
Carbonate and sulfate rocks - limestone, chalk, gypsum, anhydrite - are able to dissolve in groundwater with the formation of karst voids.
The use of sedimentary rocks in construction.
Sedimentary rocks are most often the basis for buildings and structures and are very widely used as a building material.
Coarse clastic rocks are often used as ballast material in the construction of railways and highways.
Some conglomerates and sandstones are beautiful facing materials.
The use of clays is very diverse: the manufacture of bricks, rough dishes, tiles, mineral paints, as an integral part of Portland cement.
Diatomites and tripoli are used for the production of liquid glass, various moisture-absorbing materials (sorbents), and cement.
Jasper is valued as a facing and ornamental material.
Chalk and limestone are the raw materials for lime cement. Limestone-shell rock is a wall material.
Dolomites are used as fluxes and refractories in metallurgy.
Marls are raw materials for the cement industry.
Methodology for the determination of sedimentary rocks.
Determination of sedimentary rocks should begin with an examination of appearance and effervescence with acid. First of all, it is necessary to determine the group to which the given rock belongs (detrital, chemical, organogenic).
Clay rocks have an earthy appearance. Carefully consider the texture and structure of the rock. According to the mineral composition, most of the sedimentary rocks are monomineral, ᴛ.ᴇ. are made up of one mineral. The most common minerals are quartz, opal, calcite, dolomite, and gypsum.
To study the sedimentary rocks presented in the educational collection. Complete their description in a notebook according to the plan:
1. Group by origin.
2. Name of the breed.
3. Mineral composition.
4. Coloring, fracture, density.
5. Structure.
6. Texture.
7. Engineering and geological features.
8. Application in construction.
Control questions
1. Under what conditions are sedimentary rocks formed?
2. How are sedimentary rocks classified?
3. Principles of classification of clastic rocks.
4. Structures and textures of clastic rocks.
5. Mineral composition of clastic rocks.
6. Engineering-geological properties of clastic rocks and their application.
7. What classes are chemogenic rocks divided into? Their mineral composition.
8. Structures and textures of chemogenic rocks.
9. Engineering-geological properties of chemogenic rocks and their application.
10. Engineering-geological properties of organogenic rocks and their application.
BIBLIOGRAPHY
Pavlinov V.N. and etc.
Hosted on ref.rf
Manual for laboratory studies in general geology. – M.: Nedra, 1988. p. 64-76.
LAB #4
STUDY OF METAMORPHIC ROCKS
The purpose of the work: to acquire skills in the definition of metamorphic rocks. To study the engineering and construction characteristics of metamorphic rocks and their application in construction.
Equipment: study collection of metamorphic rocks,
magnifiers, 10% hydrochloric acid solution, Mohs scale.
Conditions for the formation of metamorphic rocks.
Metamorphic rocks arise as a result of the transformation of pre-existing sedimentary, igneous and metamorphic rocks that occurs in the earth's crust. Metamorphism occurs under the influence of high temperature and pressure, as well as high-temperature vapors, gases and water. These transformations are expressed in a change in the mineral composition, structure, texture of the rock.
Metamorphic rocks are characterized by a full-crystalline structure. The most characteristic textures are: slate, banded, massive.
Metamorphic rocks are composed of minerals that are resistant to high temperatures and pressure: quartz, plagioclases, potassium feldspar, micas, hornblende, augite and calcite.
At the same time, in metamorphic rocks there are minerals that are characteristic only for this process: chlorite, garnet, talc.
Taking into account the dependence on the parent rock during metamorphism, series of rocks arise varying degrees metamorphism.
1. From sedimentary clay rocks on initial stage metamorphism, roofing schists are formed. Further intensification of metamorphism leads to complete recrystallization of the clay material with the formation of phyllites. Οʜᴎ are composed of sericite (fine-flake muscovite), chlorite and quartz. With increasing temperature and pressure, phyllites pass into crystalline schists. Given the dependence on the composition, these are mica, chlorite or chlorite-mica schists. On the highest degree metamorphism gneisses appear. Their mineral composition is microcline, plagioclase, quartz, mica, sometimes garnets, ᴛ.ᴇ. gneisses are similar in mineral composition to granites, from which they differ in their oriented gneiss texture.
2. During the metamorphism of sandstones, quartzites are formed (the mineral composition is quartz). These are strong massive breeds.
3. During metamorphism, limestones turn into marbles, which consist of calcite, have a granular-crystalline structure and a massive texture.
4. During the metamorphism of ultrabasic rocks (dunites, peridotites), serpentines (serpentinites) are formed.
5. During thermal metamorphism of sandy-argillaceous rocks, hornfelses are formed - strong fine-grained rocks of massive texture. In this case, skarns, consisting of pyroxenes and garnets, arise from carbonate rocks. These rocks are of great practical importance, since mineral deposits are confined to them - iron (Sokolovsko-Sarbaiskoye deposit), copper, molybdenum, tungsten.
Engineering-geological properties of metamorphic rocks.
Massive metamorphic rocks are highly durable, practically impermeable and, with the exception of carbonates, do not dissolve in water.
The weakening of the strength indicators occurs due to fracturing and weathering.
It is important to note that shaly rocks are characterized by anisotropic properties, ᴛ.ᴇ. strength is much lower along the schistosity than perpendicular to it. Such metamorphic rocks form thin-platy mobile talus.
The most durable and stable rocks are quartzites. Metamorphic rocks are widely used in construction. Marbles, quartzites - ϶ᴛᴏ facing material.
Roofing slates (phyllites) serve as a material for covering buildings.
Talc shale is a refractory and acid-resistant material.
Quartzite is used as a raw material for the production of refractory bricks - dinas.
Methodology for the determination of metamorphic rocks.
The definition of metamorphic rocks must begin with the establishment of their mineral composition. Next, the texture, structure, color and parent rock are determined.
To study the metamorphic rocks that are in the educational collection by external signs. Describe them in a notebook according to the following plan:
1. Name;
3. Structure and texture;
4. Mineral composition;
5. Initial breed;
6. Engineering and geological features;
7. Application in construction.
Control questions
1. How are metamorphic rocks formed?
2. What transformations occur in primary rocks during metamorphism?
3. What characteristic structures and textures are found in metamorphic rocks?
4. What minerals are typical for metamorphic rocks?
5. What factors affect the strength of metamorphic rocks?
6. How are metamorphic rocks used in construction?
BIBLIOGRAPHY
Pavlinov V.N. and etc.
Hosted on ref.rf
Manual for laboratory studies
in general geology. – M.: Nedra, 1988. p. 77-85.
LAB #5
GEOLOGICAL MAPS AND SECTIONS
The purpose of the work: to master the principle of constructing geological maps and sections. Learn to read the symbols of geological maps. Acquire the skills of determining the conditions for the occurrence of rocks on geological maps.
General information
A geological map reflects the geological structure of the earth's surface and the adjacent upper part of the earth's crust. A geological map is built on a topographic basis. On it, with the help of conventional signs, the age, composition and conditions of occurrence of rocks exposed on the earth's surface are shown.
Since more than 90% of the land surface is covered with rocks of the Quaternary age, geological maps show bedrocks without a Quaternary cover.
For construction purposes, large-scale geological maps (1:25000 and larger) are used.
When compiling geological maps, it is extremely important to know the age (geochronological) sequence of the rocks involved in the structure of the area under study.
Today, a unified geochronological scale has been created that reflects the history of the development of the earth's crust.
The following temporal and corresponding stratigraphic (stratum-layer) subdivisions are accepted in the scale (Table 6).
Geochronological and stratigraphic divisions
Table 6
Geological scale
Table 7
| Era (band) | Period (system) | Index | Duration million years | Epoch (department) | Index | Color on the map |
| Cenozoic KZ 65 Ma | Quaternary | Q | 1,7-1,8 | Holocene Pleistocene | Q 2 Q 1 | Pale gray |
| Neogene | N | Pliocene Miocene | N 2 N 1 | Yellow | ||
| Paleogene | R | Oligocene Eocene Paleocene | R 3 R 2 R 1 | orange yellow | ||
| Mesozoic MZ 170 million years | Chalky | TO | Upper Cretaceous Lower Cretaceous | K 2 K 1 | Green | |
| Jurassic | J | 55-60 | Upper Jurassic Middle Jurassic Lower Jurassic | J 3 J 2 J 1 | Blue | |
| Triassic | T | 40-45 | Upper Triassic Middle Triassic Lower Triassic | T 3 T 2 T 1 | Violet | |
| Paleozoic РZ | Permian | R | 50-60 | Upper Perm Lower Perm | R 2 R 1 | orange brown |
| Coal | WITH | 50-60 | Upper Carboniferous Medium Carboniferous Lower Carboniferous | S 3 S 2 S 1 | Grey | |
| Devonian | WITH | Upper Devonian Middle Devonian Lower Devonian | D 3 D 2 D 1 | Brown | ||
| Silurian | S | 25-30 | Upper Silurian Lower Silurian | S 2 S 1 | Grey-green (light) | |
| Ordovician | ABOUT | 45-50 | Upper Ordovician Middle Ordovician Lower Ordovician | O 3 O 2 O 1 | Olive | |
| Cambrian | Є | 90-100 | Upper-Kembirsky Middle-Kembirsky Lower-Kembirsky | Є 3 Є 2 Є 1 | Blue-green (dark) | |
| Proterozoic PR | lilac rose Classification of minerals - concept and types. Classification and features of the category "Classification of minerals" 2017, 2018. |
Currently, more than 3000 minerals are known. The basis modern classification minerals, principles are laid down that take into account the most significant features of mineral species - the chemical composition and crystal structure.
For the main unit in this classification, a mineral species is taken, which has a certain crystalline structure and a certain stable chemical composition. The mineral species may have varieties. A variety is understood to mean minerals of the same type that differ from each other in some physical feature, for example, the color of the quartz mineral in numerous varieties (black - morion, transparent - rhinestone, purple - amethyst).
Accordingly, the classification can be presented in the following form:
1. Native
2. Sulfides
3. Halides
4. Oxides and hydroxides
5. Carbonates
6. Sulfates
7. Phosphates
8. Silicates
1. Native elements (minerals).
This class includes minerals that consist of one chemical element and are named after this element. For example: native gold, sulfur, etc. All of them are divided into two groups: metals and non-metals. The first group includes native Au, Ag, Cu, Pt, Fe and some others, the second - As, Bi, S and C (diamond and graphite).
Genesis (origin) - mainly formed during endogenous processes in intrusive rocks and quartz veins, S (sulfur) - during volcanism. During exogenous processes, the destruction of rocks occurs, the release of native minerals (due to their resistance to physical and chemical influences) and their concentration in places favorable for this. Thus, placers of gold, platinum and diamond can be formed.
Application in national economy:
1- jewelry production and foreign exchange reserves (Au, Pt, Ag, diamonds);
2- cult objects and utensils (Au, Ag),
3- radio electronics (Au, Ag, Cu), nuclear, chemical industry, medicine, cutting tools - diamond;
4- agriculture - sulfur.
2. Sulfides- salts of hydrosulphuric acid.
Subdivided into simple with the general formula A m X p and sulfosalts– A m B n X p , where – A is a metal atom, B is a metal and metalloid atom, X is a sulfur atom.
Sulfides crystallize in different syngonies - cubic, hexagonal, rhombic, etc. Compared to native ones, they have a wider composition of elemental cations. Hence a greater variety of mineral species and a wider range of the same property.
Common properties for sulfides are metallic luster, low hardness (up to 4), gray and dark colors, and medium density.
At the same time, there are differences among sulfides in such properties as cleavage, hardness, and density.
Sulfides are the main source of non-ferrous metal ores, and due to impurities of rare and noble metals, the value of their use increases.
Genesis - various endogenous and exogenous processes.
3. Halides. The most widely distributed fluorides and chlorides are compounds of metal cations with monovalent fluorine and chlorine.
Fluorides are light minerals, of medium density and hardness. The representative is fluorite CaF2. Chlorides are the minerals halite and selvin (NaCl and KCl).
For halides, low hardness, crystallization in the cubic syngony, perfect cleavage, a wide range of colors, and transparency are common. Halite and sylvin have special properties - salty and bitter-salty taste.
Fluorides and chlorides differ in genesis. Fluorite is a product of endogenous processes (hydrothermal), while halite and sylvin are formed under exogenous conditions due to precipitation during evaporation in water bodies.
In the national economy, fluorite is used in optics, metallurgy, to obtain hydrofluoric acid. Halite and sylvin are used in the chemical and food industries, in medicine and agriculture, and in photography.
4. Oxides and hydroxides- represent one of the most common classes with more than 150 mineral species in which metal atoms or cations form compounds with oxygen or a hydroxyl group (OH). This is expressed by the general formula AX or ABX - where X are oxygen atoms or a hydroxyl group. The most widely represented oxides are Si, Fe, Al, Ti, Sn. Some of them also form the hydroxide form. A feature of most hydroxides is a decrease in property values compared to the oxide form of the same metal atom. A striking example is the oxide and hydroxide forms of Al.
Oxides according to their chemical composition and luster can be divided into: metallic and non-metallic. The first group is characterized by medium hardness, dark colors (black, gray, brown), medium density. An example is the minerals hematite and cassiterite. The second group is characterized by low density, high hardness 7-9, transparency, wide range of colors, lack of cleavage. Example p- minerals quartz, corundum.
In the national economy, oxides and hydroxides are most widely used to obtain Fe, Mn, Al, Sn. Transparent, crystalline varieties of corundum (sapphire and ruby) and quartz (amethyst, rock crystal, etc.) are used as precious and semi gems.
Genesis - in endogenous and exogenous processes.
5. Carbonates- salts of carbonic acid, the general formula is ACO3 - where A is Ca, Mg, Fe, etc.
General properties - crystallize in rhombic and trigonal systems (good crystalline forms and cleavage along the rhombus); low hardness 3-4, predominantly light color, reaction with acids (HCl and HNO3) to release carbon dioxide.
The most common are: calcite CaCO3, magnesite Mg CO3, dolomite CaMg (CO3) 2, siderite Fe CO3.
Carbonates with a hydroxyl group (OH): Malachite Cu2 CO3 (OH) 2 - green color and reaction with HCl, Lazurite Cu3 (CO3) 2 (OH) 2 - blue color, transparent in crystals.
The genesis of carbonates is diverse - sedimentary (chemical and biogenic), hydrothermal, metamorphic.
Carbonates are one of the main rock-forming minerals of sedimentary rocks (limestones, dolomites, etc.) and metamorphic rocks - marble, skarns. They are used in construction, optics, metallurgy, as fertilizers. Malachite is used as an ornamental stone. Large accumulations of magnesite and siderite are a source of iron and magnesium.
6. Sulfates- salts of sulfuric acid, i.e. have a SO4 radical. The most common and known sulfates are Ca, Ba, Sr, Pb. Common properties for them are i-crystallization in monoclinic and rhombic systems, light color, low hardness, vitreous luster, perfect cleavage.
Minerals: gypsum CaSO4 2H2O , anhydrite CaSO4 , barite BaSO4 (high density), celestite SrSO4 .
Formed under exogenous conditions, often together with halides. Some sulfates (barite, celestite) have a hydrothermal origin.
Application - construction, agriculture, medicine, chemical industry.
7. Phosphates- salts of phosphoric acid, i.e. containing PO4.
The number of mineral species is small, we will consider the mineral apatite Ca(PO4)3(F,Cl,OH). It forms crystalline and granular aggregates, hardness 5, hexagonal syngony, imperfect cleavage, green-blue color. Contains impurities of strontium, yttrium, rare earth elements.
The genesis is igneous and sedimentary, where it forms phosphorite in a mixture with clay particles.
Application - agricultural raw materials, chemical production and in ceramic products.
8. Silicates- the most common and diverse class of minerals (up to 800 species). Silicate taxonomy is based on the silicon-oxygen tetrahedron -4. Depending on the structure that they form when combined with each other, all silicates are divided into: island, layer, ribbon, chain and frame.
Island silicates - in them, the connection between isolated tetrahedra is carried out through cations. This group includes minerals: olivine, topaz, garnets, beryl, tourmaline.
Layered silicates - represent continuous layers, where the tetrahedra are connected by oxygen ions, and between the layers the connection is carried out through cations. Therefore, they have a common radical in the formula 4-. This group combines mica minerals: biotite, talc, muscovite, serpentine.
Chain and ribbon - tetrahedra form single or double chains (ribbons). Chain - have a common radical 4- and include a group of pyroxenes.
Ribbon silicates with a 6-radical unite minerals of the amphibole group.
Framework silicates - in them, tetrahedra are interconnected by all oxygen atoms, forming a framework with a radical. This group includes feldspars and plagioclases. Feldspars combine minerals with Na and K cations. These minerals are microcline and orthoclase. In plagioclases, Ca and Na are cations, while the ratio between these elements is not constant. Therefore, plagioclases are an isomorphic series of minerals: albite - oligoclase - andesine - labradorite - bytownite - anorthite. From albite to anorthite, the content of Ca increases.
The composition of cations in silicates most often contains: Mg, Fe, Mn, Al, Ti, Ca, K, Na, Be, less often Zr, Cr, B, Zn rare and radioactive elements. It should be noted that part of the silicon in the tetrahedra can be replaced by Al, and then we classify the minerals as aluminosilicates.
The complex chemical composition and the diversity of the crystal structure, combined, give a wide range of physical properties. Even using the example of the Mohs scale, it can be seen that the hardness of silicates is from 1 to 9.
Cleavage from very perfect to imperfect.
Often silicates are grouped by color - dark-colored, light-colored. This is especially widely applied to silicates - rock-forming minerals.
Silicates are formed mainly during the formation of igneous and metamorphic rocks in endogenous processes. A large group of clay minerals (kaolin, etc.) is formed under exogenous conditions during the weathering of silicate rocks.
Many silicates are minerals and are used in the national economy. This Construction Materials, facing, ornamental and precious stones (topaz, garnets, emerald, tourmaline, etc.), ores of metals (Be, Zr, Al) and non-metals (B), rare elements. They find application in the rubber, paper industry, as refractories and ceramic raw materials.
Along with the crystal chemical classification, there are other classifications of minerals based on other principles. For example, the genetic classification is based on the type of genesis of minerals; in the technology of processing ores, classifications are used based on their physical (separating) properties, for example, by magnetism, density, solubility, fusibility, and other features.
Quartz - SiO 2. The modification stable at low temperatures is usually called simple quartz. Diagnostic features. Quartz crystals are diagnosed by shape, hardness, conchoidal fracture, and lack of cleavage. Quartz can be confused with chalcedony, feldspar, nepheline and topaz. Origin. About 65% of the earth's crust consists of quartz, it is called ubiquitous, rock-forming. In many intrusive and effusive felsic igneous rocks, it is almost the main mineral. Included in pegmatites, present in many metamorphic rocks. In significant masses, as a vein mineral, it is common in hydrothermal deposits. It is also present in sedimentary rocks (quartz sands, quartz sandstones, quartz conglomerates). Chemical composition. Varieties painted in other colors have a variety of impurities or inclusions of other minerals. Syngony quartz is trigonal, and the high-temperature modification a - quartz is hexagonal. appearance crystals are more often hexagonally dipyramidal. The edges of the prism are often shortened or absent. Very large crystals are known. A crystal weighing 70 tons was found in Kazakhstan. The faces of the crystals are covered with transverse shading. in nature, drusen, brushes, granular masses. Quartz is characterized by twinning, and crystals grow together according to different laws, twins are Dauphine, Brazilian, Japanese. Color may be very different. Transparent and translucent varieties have different names: 1) mountain crystal- colorless water-transparent crystals; 2) amethyst- purple, lilac, lilac, raspberry, transparent; 3) rauchtopaz- smoky, painted in grayish or brownish tones; 4) morion— painted in black; 5) citrine- golden yellow or lemon yellow; 6) prase- greenish quartz; 7) pink quartz; 8) milky- white quartz; 9) aventurine(spark). Bl e sk glass. Hardness 7. Cleavage absent. Density 2.5 - 2.8. Other properties. Able to transmit ultraviolet rays, is a piezoelectric. Molten quartz solidifies easily and forms a quartz glass (amorphous quartz). Practical use. Its application is varied. Beautiful varieties are used in jewelry. Pure crystals with unique properties are used in electronics, ultrasonic technology, and optical instrumentation. Rauchtopaz, rock crystal, morion is used as a radio wave stabilizer. Rock crystal is used in telemechanics, automation, high-quality generators. Pure low-iron quartz sands serve as an excellent raw material in the glass-ceramic industry, for the production of carborundum (SiC). Carborundum or silicon carbide is a first-class abrasive material. Quartz sands of fine fractions are used in sandblasting machines for polishing stone and metal products, as well as for sawing rocks. Place of Birth. There are deposits of quartz in the Urals, the so-called "crystal cellars" containing rock crystal, morion , amethyst, topaz, etc. are found in Primorye, Yakutia. The White Sea amethyst from Cape Ship is known on the Kola Peninsula. Pegmatite veins with quartz crystals are common in Aldan, Pamir, Volhynia. Rock crystal is mined in Yakutia (Bolshaya Khatyma). Brazil supplies natural quartz crystals for industry. There is quartz in Sri Lanka, India, Burma, Uruguay, Switzerland, Madagascar and other regions. The museum has over 700 samples of quartz and its varieties. A wide variety of crystals weighing from 440 kg to 1 g (scepter-shaped, with figures of growth, etc.) are widely represented, there are druses, brushes, vein quartz, quartz with other minerals. The richest Ural collection of quartz: mountains. crystal from the Gumbeiki, Berezovskoye, Astafyevo deposits; morion from Murzinka; quartz-prazem, quartz with chlorite and adularia, and “hairy” quartz from the Subpolar Urals; pink quartz (Gumbeika); intergrowths of crystals from Mias, Pyshma, Nagla. Beautiful Druzes from Kamchatka and the Chukotka Peninsula (Iultinskoe); quartz with zinc blende (England); quartz with rubellite from the Chita region (Borshchevochny ridge). There is quartz from Transbaikalia (Adun-Cholong), from Mangystau; sintered quartz from Kirghizia, pink quartz from Altai (Tigeretskiye squirrels, Kolyvan), the Urals (Gumbeika), and South Africa.