How many groups of minerals are there?

The reference table contains a classification of mineral groups – native elements, sulfides, sulfates, halides, phosphates, carbonates, oxides and silicates, and a brief description.

Mineral group table

Groups of minerals can be divided based on their crystal structure and chemical composition. Characteristics of classification groups I. Native elements These are chemically inert minerals under natural conditions – the composition of which generally corresponds to individual elements, but they may contain various impurities, including such as alloys and solid solutions. There are approximately 90 such minerals, which make up about 0,1% of the weight of the earth’s crust. These are mainly rare and very rare minerals. Their origin is both endogenous and hypergenic. Native elements include both metals (gold, platinum, copper, silver) and non-metals (diamond, graphite, sulfur, arsenic). There are about 200 minerals of this group (about 0,25% of the weight of the earth’s crust). The most common are pyrite and pyrrhotite. This class includes not only sulfides, but also selenium, arsenic, telluride, antimony and other similar compounds of heavy metals. There is no water in these compounds. Characteristic features: high specific gravity, metallic luster, usually low hardness, typical color for metals – steel-gray, brass-yellow, silver-white, etc. The origin is most often hydrothermal, vein, but can be contact-metamorphic and supergene. Many sulfides (sphalerite, galena, chalcopyrite, cinnabar and others) are the most important ore minerals. This group includes up to 260 minerals (0,1% of the weight of the earth’s crust), which are salts of sulfuric acid. Among them there are basic and aqueous salts. Mostly light-colored, low-hardness minerals that form thick layers of chemical sediments and oxidation products of sulfides and sulfur. Due to their good solubility, they easily lose and add water, are redeposited, and are involved in diagenesis. These are chloride, fluoride and iodide compounds that form about 100 minerals, which are salts of hydrohalic acids. Of these, fluorine and chlorine compounds are the most common. The most common chlorides are sodium, potassium and magnesium salts. They are mostly colorless, but can be slightly colored by impurities of iron, copper, and lead oxides; Easily dissolves in water and is palpable to the taste. Copper chlorides are green or blue. Lead chlorides are heavy and have a diamond luster. Hardness 2-3. According to their genesis, these are chemical sediments of arid environments (Na, K, Mg salts) and products of hypergenesis in the sulfide oxidation zone (Cu, Pb salts and others). The most important of the chloride salts are NaCl – halite, which makes up the thickness of table salt, as well as K and Mg salts. The most common fluoride is fluorite (CaF₂). Fluoride minerals are light in color, with low specific gravity and hardness. Most often their genesis is magmatic, pneumatolytic and hydrothermal, but some Ca and Al fluorides can occur in the hypergenesis zone. Phosphates, together with arsenates and vanadates by mass, make up 0,7% of the earth’s crust (about 350 minerals). These are basic and aqueous salts of phosphoric acid. Many minerals are very rare and difficult to diagnose. Most are inert, forming in the surface zone with the participation of organic matter, although they can also be deep. These are salts of carbonic acid; constitute up to approximately 1,8% of the mass of the earth’s crust. About 80 minerals are known, but the most common are Ca and Mg carbonates. They are distinguished by low hardness, non-metallic luster, and light color. Specific gravity is determined by chemical composition. All carbonates boil quite easily in hydrochloric acid, releasing CO₂. This is their main diagnostic sign. Mostly hypergene, biogenic. Hydrothermal carbonates are confined to veins, zones of contact metasomatism, can form tonsils in effusive rocks, and are released from mineral springs. They accumulate in modern seas and oceans, controlling the carbon dioxide system of these reservoirs. They are of great practical importance in the form of ore and as a building material. Approximately 200 oxide minerals make up approximately 17% of the earth’s crust. The most common oxide is quartz (13%). Iron oxides are also quite widespread (more than 3%). This is the most important rock-forming group of minerals. They often occur in the form of well-formed crystals, but can also be cryptocrystalline and amorphous. Subject to isomorphism. There are almost no minerals with a metallic luster among the oxides. The structures are different, reflected in a variety of properties. Hardness is usually more than 5,5. They are formed during endogenous and exogenous processes. The hardest and most stable accumulate in placers. Many oxides are the most important ores of iron, chromium, manganese, aluminum, titanium, tin, tantalum, uranium, and rare earths. Silicates are the most numerous (about 800) group of rock-forming minerals, making up up to 80% of the mass of the earth’s crust. Silicates have complex chemical properties. compound. Their main components are Si, Al, Fe, Mg, Ca, Na, K, less often – Mn, Fi, B and others. The main structural element of silicates is the silicon-oxygen tetrahedron [SiO₄] 4- . The type of structure is determined by the nature of the combination of tetrahedra. Silicates with island, chain, sheet and frame structures are distinguished. Island silicates are composed of single radicals of orthosilicic acid H₄[SiO₄], isolated pairs of tetrahedra having one common oxygen, isolated calcium groups of three [Si₃O₉] 6-, four [Si₄O₁₂] 8- and six [Si₆O₁₈] 12-ring groups. Chain silicates – the structure consists of separate chains in which each tetrahedron has two common oxygens. The radical of such a structure is [Si₄O₁₂] 4- or [SiO₃] 2- . Belt silicates have a double chain structure. Radical – [Si₄O₁₁] 6- . Sheet silicates – silicon-oxygen tetrahedra form sheets. Radical – [Si₂O₅] 2- . Framework silicates are a complex structure in which the oxygens of all tetrahedra are common. In a pure structure of this type there are no free valences. But silicon in the centers of tetrahedrons can be partially replaced by aluminum, which releases one valence. Silicates clearly demonstrate the relationship between structure and physical properties. By genesis, silicates are mostly associated with endogenous processes, but weathering of silicates leads to the emergence of others. ____________ The source of information: 1. DICTIONARY OF GEOLOGICAL TERMS AND CONCEPTS./ – Tomsk: 1996. 2. Z.K. Azizov, S.A. Pyankov Determinant of minerals: Textbook / Ulyanovsk Technical University. -Ulyanovsk, 2006 Share the link with your friends: MANUFACTURER
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Elements of the earth’s crust Planet Earth can be divided into three main layers. The first and innermost is the core. The other is the mantle, which is the middle layer, and in its upper part it is already included in the lithosphere, i.e. the outer shell of the Earth. The last, outermost layer is the earth’s crust. Its thickness varies from 10 to 70 kilometers, and makes up only 1,4% of the volume and 0,3% of the mass of this planet. Despite this, the geosphere is the most diverse physically and chemically. The combination of geographical and chemical sciences laid the foundation for the creation of geology – a branch of exact sciences that studies the structure, properties and history of the development of planets. Thanks to the development of this science, it is possible to determine, among other things, the chemical composition of the earth’s crust. Published: 31-03-2023

Formation of the Earth

As a result of ongoing plate tectonic movements, rock formation processes can take up to millions of years. Due to various displacements of rocks that occurred in history, many layers were removed from the surface into the bowels, giving way to later formed rocks, or vice versa – from the bowels they were pushed out to the surface of the planet. Thanks to this, geologists can study not only the rocks that make up the surface layer, but also those that were previously formed and were located at a depth of several kilometers. Since deeper layers are unreachable due to the conditions existing there, i.e. high pressure and temperature up to 6000 o C in the core, all information about them was obtained by indirect methods, using phenomena such as seismic waves, earthquakes and volcanic eruptions. On the other hand, thanks to relatively easy access to the geosphere at a depth of about 16 km, it is possible to determine the average chemical composition of the lithosphere, and therefore the earth’s crust.

Earth’s crust

This outermost layer of the Earth is also the most diverse and best known to us. This is the geosphere with the lowest temperature, thickness and mass. From the inside, the earth’s crust borders the mantle through the Mohorovicic boundary, and from the outside it is in direct contact with the atmosphere or hydrosphere. The chemical composition of the earth’s crust includes 93 elements, but only 8 of them account for up to 99,5% of its mass. It is assumed that in mass percentage oxygen occupies 46,6%, silicon – 27,72%, aluminum – 8,13%, iron – 5,00%, calcium – 3,63%, sodium – 2,83%, potassium – 2,60% and magnesium – 2,08%. In comparison, hydrogen content is estimated at 0,14%, sulfur 0,05%, carbon 0,03% and copper 0,01%. The composition also includes chlorine, rubidium, fluorine, strontium, barium, nickel, lithium, nitrogen and many others. The diversity of this geosphere is the result of the predominance of many structures such as igneous, metamorphic and sedimentary rocks in many configurations. Due to the above-mentioned geological processes, the resulting rocks are not characterized by the same chemical composition. It is heterogeneous both horizontally and vertically. In addition, it is very rare that an element is found in its native form; usually they form clusters of different atoms in the form of minerals. Some of them, such as gold, silver, copper, sulfur, diamond and graphite, can occur as a single element. However, there are many more multi-element minerals, the estimated number currently known is 3000, with silicates considered the most common.

Minerals

By definition, these are chemical compounds formed as a result of natural processes that have a specific chemical composition and crystal structure. Depending on the type, we can distinguish them by different chemical and physical properties. There are many types of minerals because a single chemical compound can exist in different crystalline forms. For example, calcium carbonate forms three minerals with the same chemical properties but different physical properties – chalk, limestone and marble. According to the Nickel-Strunz classification, minerals can be divided into nine categories: native elements, sulfides, halides, oxides and hydroxides, nitrates, carbonates and borates, sulfates, chromates, molybdates, tungstates, phosphates, arsenates, vanadates, silicates, organic compounds. Minerals that have the most common elements in their structure are rock-forming.

Rocks

The term “rock” refers to massive accumulations of minerals. The mineral composition of rocks can be very diverse. There are monomineral varieties such as calcitic limestones or marbles, called monomineral rocks. However, the vast majority are polymineral rocks, consisting of at least two minerals. Typically found, for example, are calcareous rocks, which are composed of limestone, and granite rocks, in which the main mineral is quartz. The most common are silicates, which make up three-quarters of the earth’s crust. They are found in the form of rocks, sands, soils and clays, and their composition is dominated by silica and salts of silicic acids.

Examples of ores

The same group with sulfides includes similar sulfur salts, arsenides, antimonides, bismuths, selenides and tellurides. They have similar physical properties, including high density and strong metallic luster. Most of them form from hydrothermal solutions, but can also crystallize from sulfide magma. Despite their not very high prevalence at the level of 0,15 percent of the mass of the earth’s crust, due to the ores of valuable metals (gold, silver, platinum), they are of economic importance. This group of minerals includes, in particular: alabandine MnS, stibnite Sb₂S₃, arsenopyrite FeAsS and cinnabar HgS. The category of halides includes mainly chlorine and fluorine compounds; bromides and iodides are less common. A characteristic feature of light metal halides is glassy luster and low refractive index. They are most often found in pegmatites and hydrothermal veins. They are used in the production of mineral fertilizers, chemical raw materials and fluxes, some of which are also consumed directly. Examples of minerals of this group are halite NaCl, fluorite Ca₂F, sylvite KCl and atacamite Cu₂(OH)₃Cl. Despite the greatest abundance of the element oxygen in the earth’s crust, its mineral resources account for only 4,5%. Almost all of them consist of oxide iron ore, and other compounds are oxides of aluminum, magnesium, titanium and chromium. Minerals of this group are formed under magmatic, hydrothermal and atmospheric conditions. Some of them are important industrial raw materials, others are valuable gemstones. These include chromite FeCr₂O₄, Fe hematite₂O₃, ruby ​​and sapphire Al₂O₃. Sulfates and chromates are a very large group of almost 200 minerals. They are characterized by transparency and glassy luster. They are formed at low temperatures and pressures in conditions enriched with oxygen. This group includes gypsum CaSO₄· 2H₂O, anhydrite CaSO₄ and celestine SrSO₄. There are about 70 carbonates in nature, and the most important of them is calcite, which can form sedimentary, metamorphic and igneous rocks. As well as limestones, marbles and carbonatites. They usually form in hydrothermal veins and sedimentary basins. Like iron, manganese and zinc ores, they are of great importance due to their use in the chemical, metallurgical and cement industries. Carbonate minerals include aragonite and calcite CaCO₃, azurite Cu₃(CO₃)₂(OH)₂, dolomite CaMg(CO₃)₂ and magnesite MgCO₃.