Tin is one of the earliest metals discovered and used by humans. It is silver-white at room temperature and has three allotropes with temperature changes. Below 13.2°C it is α tin (grey tin), 13.2-161°C is β tin (white tin), and above 161°C it is γ tin (brittle tin). Gray tin belongs to the diamond-type equiaxed crystal system, white tin belongs to the tetragonal crystal system, and brittle tin belongs to the orthorhombic crystal system. A protective film of tin dioxide is formed on the surface of tin in the air and is stable. The oxidation reaction is accelerated under heating, and tin reacts with halogen to form tin tetrahalide, which can also react with sulfur. Tin can slowly dissolve in dilute acid and quickly dissolve in concentrated acid. Tin can be dissolved in strong alkaline solution. Tin will be corroded in acidic solutions of salts such as ferric chloride and zinc chloride.
Tin is a copper-philic element, but in the upper part of the lithosphere, it has the characteristics of both oxygen and sulfur affinity. There are more than 50 tin-containing minerals known in nature. At present, cassiterite is mainly of economic significance, followed by kesterite. In some deposits, sulphur-tin-lead ore, stibnite, cylindrical tin ore, and sometimes black sulphur-silver-tin ore, black boron-tin ore, Malayanite, schistite, brucite, etc. can also be relatively rich. Set, has industrial value.
Cassiterite, the chemical composition is SnO2, tetragonal crystal system, the crystal is in the shape of double cones, cones, and sometimes needles. It often contains mixed substances such as iron, niobium, and tantalum. In addition, it can also contain manganese, scandium, titanium, zirconium, tungsten, and dispersed elements such as iridium and gallium. The presence of Fe3+ often affects the magnetism, color and specific gravity of cassiterite. Cassiterite is the main raw material source of tin.
Kesterite, also known as tetrahedronite, has a chemical composition of Cu2FeSnS4, tetragonal crystal system, rare crystals, and pseudotetrahedron, pseudooctahedron, plate-like shapes. Yellow tin deposits are more common in Guangxi tin-bearing sulfide metasomatic deposits and filling-type tungsten-tin deposits, and Hunan high-middle-temperature hydrothermal type lead-zinc deposits.
The antimony tin-lead ore has a chemical composition of Pb5Sb2Sn3S14, with iron, zinc, etc. mixed in the composition. The crystal is thin, often curved, and the twin crystals are complex. The aggregates are massive, radial or spherical. It is produced together with stibnite and kesterite, and is also produced in tin ore veins.
Sulfur tin lead ore, chemical composition is PbSnS2, orthorhombic crystal system, the crystal is plate-like, the shape is close to square, usually a massive aggregate. It is often produced in tin ore veins together with cassiterite, galena, sphalerite, and pyrite.
Cylindrical tin ore, with a chemical composition of Pb3Sb2Sn4S14, orthorhombic crystal system, a cylindrical or massive and spherical aggregate, is produced in tin ore veins together with stibnite, sphalerite and pyrite.
Pure tin interacts slowly with weak organic acids, so it is often used in the manufacture of tin-plated sheets, commonly known as tinplate, and used as food packaging materials. Pure tin can also be used as a coating for certain mechanical parts. Tin is easily processed into tubes, foils, wires, strips, etc., and can also be made into fine powder for powder metallurgy. Tin can be alloyed with almost all metals, and solder, tin bronze, babbitt alloy, lead-tin bearing alloy and lead alloy are more commonly used. There are also many tin-containing special alloys, such as zirconium-based alloys, used as nuclear fuel coating materials in the atomic energy industry; titanium-based alloys, used in aviation, shipbuilding, atomic energy, chemical, medical equipment and other industries; niobium-tin intermetallic compounds can be used as super The conductive material, tin-silver amalgam is used as a dental metal material. The important compounds of tin are tin dioxide, tin dichloride, tin tetrachloride and tin organic compounds. They are used as raw materials for ceramic enamel, mordant for printing and dyeing silk fabrics, heat stabilizer for plastics, and as bactericides. And pesticides.
my country’s tin ore resources have the following characteristics: (1) The reserves are highly concentrated. my country’s tin mines are mainly concentrated in 6 provinces, namely, Yunnan, Guangxi, Guangdong, Hunan, Inner Mongolia, and Jiangxi. Yunnan is mainly concentrated in Gejiu, and Guangxi is concentrated in Dachang. The reserves of Gejiu and Dachang account for the total reserves of the country. About 40% of reserves. (2) Primarily tin ore is the main source, and placer tin ore plays a secondary role. In the country’s total reserves, primary tin ore accounts for 80%, and placer tin ore accounts for only 16%. (3) There are many co-associated components, only 12% appearing in the form of a single mineral. Tin ore as the main mineral accounts for 66% of the country’s total reserves, and tin ore as a co-associated component accounts for 22% of the country’s total reserves. Symbiotic and associated minerals include copper, lead, zinc, tungsten, antimony, molybdenum, bismuth, silver, niobium, tantalum, beryllium, indium, gallium, germanium, cadmium, and iron, sulfur, arsenic, fluorite, etc. (4) There are many large and medium-sized deposits, especially Gejiu in Yunnan and Dachang in Guangxi, which are world-class polymetallic super-large tin mining areas.
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Post time: Aug-30-2021