The mineral fluorine with the chemical formula CaF 2 is the most important mineral fluoride in nature. From which the element fluorine can be obtained. The mineral is found in yellow, green, pink, purple, blue, colorless and sometimes black. The fluorine mineral, if pure, has 48.7% fluorine and 51.3% calcium. Fluorine is an economically important mineral and is often associated with important minerals such as sphalerite, barite, galena and..
Fluorine structure:
The structure of fluorine is one of the binary structures of materials in which the anions are in the form of a simple cube and the cations are placed in half of the octagonal cavities. This network can be described from another point of view in which the cations have a cubic arrangement with full center faces and the anions are placed in quadrilateral cavities.
Properties of fluorine mineral:
Crystallization system: isometric
Shape of crystals: hexaider, octahedron, compound, rhomboider and dodecahedron
Appearance: Fluorite crystals are seen as fine and coarse grains and compact and jelly, filamentous, radial, coating, flat and granular aggregates.
Physical properties:
Full face - Hardness 4 on mouse scale - Specific weight 2/3 - 3 grams per cubic centimeter - Clear to semi-transparent - Polished glass - The color of this mineral has many changes - White soil color - Refractive index 1/434 - Melting point 1402 and boiling point 2513 ° C.
chemical properties :
Soluble in HF and H2SO4
Chemical composition: Ca: 51.33%, F: 48.67% with rare Cl inclusions
Other specifications: Dark purple luminescence, blue to purple fluorescence and sometimes thermoluminescent brown
Criteria for detection: It is usually known by cubic crystals and octagonal faces, glass polish and beautiful colors and line drawing with a knife.
Paragenesis: galena, sphalerite, calcite, dolomite, barite, apatite, cassiterite, quartz and tourmaline
Types of fluorine ores:
Vein type
Fluorite-containing veins have been reported in acidic-intermediate, metamorphic and sedimentary igneous rocks. Fluorite veins are mostly associated with quartz, calcite, barite, galena and sphalerite. The economic grade of the veins varies and ranges from 25 to 65%.
Stratiform type
Stratiform type fluorite deposits are formed in carbonate rocks. No igneous rocks have been reported in the Illinois state fluorite deposits, while porphyry granite masses have penetrated the Mexican fluorite deposits formed in carbonate rocks. Minerals associated with fluorite are: calcite, dolomite, quartz, galena, barite and celestite. The fluorine content is at least 15%.
Substitution type:
Fluorite deposits are a type of substitution reported in carbonate rocks adjacent to acidic masses from Mexico. Mexico has the largest and richest reserves of fluorine.
Type of stockwork
Stockwork-type fluorite deposits are associated with granite intrusions and have been discovered in New Mexico, Colorado, and South Africa. The expansion of one of these reserves is 70 to 200 meters and its depth is up to 900 meters. The fluorine content is 14%.
Fluorite with alkaline-carbonate complexes
The element fluorine is geochemically closely related to alkaline magmas and carbonates. Fluoride-rich magmatic solutions originate from alkaline, super-alkaline and carbonate rocks. Fluorite deposits are often located in intercontinental rifts. Fluorine mineralization is found in these complexes, but those of economic value are formed at a distance from the intrusive mass.
Type of penetration cutting
Magmatic solutions under special conditions lead to the formation of intrusive incisions. If this solution is rich in fluorine, it will cause storage.
Fluorine is left
Fluorite in granite, carbonate rocks or veins is released by weathering and remains in place, and other minerals are often altered and transported due to weathering.
Fluorite with pegmatites
Some pegmatites that contain fluorine. When concentrated, fluorine forms a good reserve
Fluorine mineralization
Florin
Mercury, antimony, fluorite
Metal complex, fluorite
Rare metal, fluorite
Beryllium, fluorite
Rare earth metal, fluorite
The first, second and fourth types have active tectonic and geosynclinal magmatic regions, the fifth and sixth types have active tectonic magmatic regions, and the third type has crustal extensions in all three.
Geology and dispersion of fluorite mineral
Fluorite is found in a wide range of geological environments, indicating the formation of this mineral under a variety of physical and chemical conditions. On the one hand, it exists as a minor mineral in granites and igneous rocks, and on the other hand, it is seen as a crystal in geodes and as a cluster in limestone caves. This mineral is usually associated with important deposits of lead, zinc and barite and is therefore of particular importance. This is because exploration and exploration can lead to the discovery of these deposits, which in turn makes fluorine deposits more valuable. Sometimes the presence of fluorite itself makes other mineral deposits more valuable. Therefore, in technical-economic studies of lead, zinc, barite and fluorite deposits, special attention should be paid to associated minerals. Because these minerals may have a great impact on the economics of an deposit.
Extractable by-product in metal deposits
Fluorite is found as a major by-product of lead and zinc in various parts of the world. In some of these deposits, the average grade of fluorite reaches 10 to 20%, which can be extracted economically. For example, in a lead and zinc plant in Mexico, fluorite is produced on a large scale using factory waste materials.
Fluorine has also been found in pegmatite environments, open space fillings, shear kiln fillings, and lake sediments.
Conditions of formation and genesis of fluorite
Fluorite is formed and observed in a wide range of geological conditions. Also in the form of fluorinated quartz veins in igneous, sedimentary and metamorphic rocks, substitution in skarns, in the center of the marginal part of carbonates, in tailings deposits of base metals and barite ore, substitution in limestones, pegmatite veins and furnaces A cut is seen.
In this way, it accompanies the main minerals of the granite family and the nearby rocks of this family and is found completely in the nodes and limestones inside the caves.روشهای Major fluorite extraction
Surface ores are extracted by standard open methods and by scrapers and other machines. In deeper deposits, depending on their type, the room-base method is used for layered deposits and the open drainage or extraction method is used for deeper vein deposits.
Factors such as the shape, size, depth and type of storage and the concentration behavior of the mineral at depth play a very important role in determining the proper extraction method from fluorine reserves. Geotechnical information such as the status of ores and embedded rocks, faults, joints, surface and deep water, and floor pressure should also be considered.
Since most fluorite deposits are layered or streaked and some are lens-shaped, the open or underground method is used depending on the concentration gradient.
The resistance of embedded rocks in choosing one of the above two methods is one of the important factors. Fluorite is extracted in two ways in open pit extraction method. For surface and aerated reserves and shallow shallow deposits it is extracted by bulldozers, loaders and for deeper deposits it is extracted in stages by the same machines and mineral trucks.
Applications of mineral fluorine
Fluorite was used by the ancient Greeks to make decorative utensils such as cups, glasses and table tops. Today, fluorite is the basic material of the aluminum, chemical and steel industries in the world. Fluorine is used in the preparation of hydrofluoric acid and its derivatives, as well as in the nuclear, ceramic, casting, ferroalloy, and other industries. Fluorite is used to make synthetic Na3AlF6 cryolite, which is essential for smelting aluminum. Fluoridric acid is also used as a catalyst in the preparation of high octane fuels, corrosives and glass polishes.
Transparent and light colors of fluorite are used in the manufacture of glass and lenses. This mineral is also used in the pottery, enamel and ceramic industries made of fiberglass and cosmetics. The purity of this type of fluorite is between 95 and 96%. Colorful and transparent fluorines can also be used as an ornamental mineral.
Fluorine classification based on type of application
Half of the fluorite produced is used in the iron and steel industries. Fluorine is divided into three categories: acidic, ceramic and metallurgical.
Degree of acidity (CaF2: 97%) (SiO2: 1-1.5%) (Sulfur: 0.03-0.1%) and absence of barium, lead and sulfur.
This type of fluorite is used to prepare hydrofluoric acid. This acid plays a fundamental role in the aluminum industry as well as the related chemical industries.
Ceramic grade (CaF2: 95-96%) and (CaF2: 80-92%)
Used to make special glass and glaze. Fluorite is used in the preparation of white and colorless opal glassware and flintite glass. Mixing 10% to 30% fluorine with glass causes it to turn white and cloudy.
Metallurgical degree
(CaF2) (Sulfid <0.3%) and (Pb <0.05%) or (Pb: 0.25-0.5%)
Used in metalworking industries. Fluoride consumption in this industry is between 1 to 10 kg per ton. Fluorite causes more slag flow and facilitates the transfer of sulfur and phosphorus to the slag.
Application in nuclear industry
The hexafluoride compound is used to separate U235 from U238. The most common methods of enrichment are gas diffusion and centrifuge enrichment. Gaseous diffusion enrichment is a process in which uranium hexafluoride under force is passed through a series of special porous gas barrier shields, the isotopes are separated, and the lighter molecules move faster and adhere to the inhibitors more than the heavier molecules.
Application in fluoridation of drinking water
The presence of 1 ppm of fluoride in water easily prevents tooth decay, is completely safe and harmless, and reduces tooth decay by up to 60%.
Most developed countries use fluoridated water. Some fluoride sources used for fluoridated water include (Na2SiF6), silicic acid (H4O4Si), silica hexafluoride (H2SiF6), and natural fluorescein.Environmental impacts
Teeth and bones are made up of a combination of calcium phosphate minerals such as apatite. The entry and intervention of fluorite into the structural crystals of apatite reduces its solubility and increases its hardness, and of course increases the resistance to tooth decay and osteoporosis. Fluoroapatite has been considered because of its high similarity to the mineral structure of bones and teeth and also as a rich source of fluoride in the repair and treatment of bone and tooth defects. Therefore, the effect of fluorine in reducing dental diseases, especially tooth decay, is seen. This problem was initially diagnosed based on regional differences in the incidence of tooth decay. The average concentration of fluorite in crustal rocks is about a few ppm. The normal concentration obtained from the presence of fluorite in drinking water is about one ppm and its lethal and harmful amount is about 4 grams. Receiving very high amounts of fluorite (twenty to forty times normal) causes abnormal development and hardening of the bones and calcification of the ligaments (fluorescence disease).
Therefore, people who use drinking water with a concentration as low as one ppm of fluorite are less likely to develop tooth decay. But excessive use of fluorite will also have side effects. In areas where natural waters normally have high levels of fluorite, and as a result the intake increases to two to eight times the normal level, black and dark spots can be seen on the teeth. Therefore, the presence of high doses of fluoride in drinking water is toxic but is useful in low concentrations.
In industries that require fluoride and high temperature processes are in place, fluorine is released into the environment as fluoride acid or similar compounds, which is highly toxic to plants, animals, and humans.
Certain compounds of fluoride, such as CFCs, also deplete the ozone layer. For this purpose, in the Montreal Protocol, the use of alternatives for them was considered. Alternatives such as hydrochlorofluorocarbons have a lifespan of 2-28 years, which is much more suitable than that of CFCs with a lifespan of 400-60 years. In addition, these alternatives react with OH in the lower layers of the atmosphere and do not concentrate. As a result, the potential for ozone depletion of these alternatives is 0.1-0.02 or zero, compared to CFCs with a potential of 0.4-1.
