CASSITERITE
The aggregates are mostly granular blocks. The outer shell has a grape-like shape and has a concentric radial fibrous structure inside, which is called wood cassiterite. Pure cassiterite is almost colorless, but generally yellowish brown to brownish black; streaks are white. Diamond shiny, shiny grease on the fracture. Most of the cassiterite is mined from the sand mine. China, Malaysia, Indonesia, Bolivia, the former Soviet Union, Thailand, etc. are the major producers of cassiterite. China's production areas are mainly distributed in Yunnan, Guangxi and Nanling, among which the southwestern Danda plant is the largest. Yunnan Gejiu Tin Mine has a long history of mining and is known as the “Sidu” in China.
Introduction
Tin is an indispensable metal for human production and life, and one of the first metals discovered and used in human history. Tin has the advantages of low melting point, corrosion resistance and easy change of other metal properties. It is widely used in various fields of the national economy and can be used in nuclear power generation, aircraft engines and other technical fields. At present, the demand for tin in the world continues to grow, and the consumption level of tin has become one of the indicators for measuring the level of industrial development in a country. Therefore, it is of great significance to strengthen the development and utilization of tin resources. The average content of tin in the earth's crust is 0. 004%, and the basic reserves of tin resources in the world are about 10 million tons, of which more than 75% of tin is derived from cassiterite.
Tin sulphate contains 78.6% tin, which is the most common tin mineral and the most important ore mineral of tin. The cassiterite is mainly produced in the hydrothermal veins of the granite intrusion or near the surrounding rock of the rock mass, and is also often distributed in the pegmatite and the granite itself.
Because of its high hardness, large specific gravity and strong chemical weathering resistance, it is often integrated with sand ore, called sand tin. Most of the cassiterite is mined from the sand mine. China, Malaysia, Indonesia, Bolivia, the former Soviet Union, Thailand, etc. are the major producers of cassiterite. China's production areas are mainly distributed in Yunnan, Guangxi and Nanling, among which the southwestern Danda plant is the largest.
Yunnan Gejiu Tin Mine has a long history of mining and is known as the “Sidu” in China.
Tetragonal system, irregular granular aggregate.
Color: bright dark brown, visible colorless, yellow and black
Gloss and transparency: diamond to yam diamond, opaque to transparent
Mohs hardness: 6~7
Cleavage: Incomplete
Density: gem grade up to 6.87~7.03
Photographic characteristics: one-axis crystal, positive light
Polychromism: none
Refractive index: 1.997~2.093 (+0.009, -0.006)
Birefringence: 0.096~0.098
UV fluorescence: none
Absorption spectrum: no characteristics
Tin mine and stone
2. Refers to ore
3. The name of the ore. Is the main raw material for refining pure tin
Structure and morphology
Tetragonal system, a0 = 0.4737 nm, c0 = 0.3185 nm; Z = 2. Rutile structure. Zr instead of Sn leads to an increase in lattice constant.
Complex tetragonal double cone crystal, D4h-4/mmm (L44L25PC). Crystals often have a double-cone shape, a double-tapered column shape, and sometimes a needle shape. The main simplex: quadrilateral double cone s, e, square column m, a, sometimes visible complex square column r and complex square double cone z. There are fine vertical lines on the cylinder. According to (011), the twin crystal faces form a knee-shaped twin crystal.
The aggregates are often irregularly granular. The fibrous cassiterite formed by the colloidal solution is called wood-tin, which is grape-like or stalactite-like, and has a concentric band structure.
The shape of cassiterite has a metrical significance. Generally, the formation temperature is high, and the crystal habit tends to be equiaxed or short columnar; the low temperature tends to be long columnar or needle-like.
Physical properties
Colorless is rare, generally brown due to inclusions, black when Fe is high, asphalt black if Nb, Ta is high, and ultra-microscopic inclusions containing coltan and coltan may cause color Evenly. The streaks are white to light brown. translucent. Diamond shiny, broken grease luster. The cleavage is not complete. It has a split and the fracture is uneven to the shape of a shell. Crisp. Hardness 6~7. The relative density is 6.8~7.0. Generally non-magnetic, iron-rich cassiterite can be electromagnetic.
Under the polarizer: colorless, light yellow, light brown or reddish, sometimes the color distribution is uneven, in the shape of dots or rings. One axis crystal, high refractive index, No = 1.9836 ~ 2.0475, Ne = 2.0818 ~ 2.1397. Sometimes optical anomalies occur, biaxial crystals, 2V = 0 to 38?. The pleochroism is uncertain.
Crystal chemistry
It is often mixed with Fe, Nb, and Ta, and may contain Mn, Sc, Ti, Zr, W, and dispersing elements In, Ga, Ge, and the like. Nb5 and Ta5 can replace Sn4 in a heterogeneous analogy. But more is the existence of ultra-microscopic inclusions such as coltan and coltan.
Birth and combination
Endogenous cassiterite deposits are often produced in the volcanic lithology of the granitoids (the decomposition of potassium feldspar into muscovite and quartz). Due to the action of volatile matter, tin is transported by SnF4 and SnCl4, and then hydrolyzed to form cassiterite:
SnF4 2H2O-2SnO2 4HF
In the granitic pegmatite veins, cassiterite is symbiotic with quartz, micro-plagioclase, albite, muscovite, etc., sometimes with huangyu, spodumene, tourmaline and the like. In such deposits, the distribution of cassiterite is often uneven, and the general grade is not high, but it can be combined with rare metals such as Li, Rb, Cs and Be.
The hydrothermal type cassiterite deposit has important industrial significance.
Contact with the metamorphic cassiterite deposit is related to the late hydrothermal activity.
Identification feature
Crystal form, twin crystal, color, hardness and the like are similar to rutile, but the density of cassiterite is large, the cleavage is poor, and the refractive index is lower than that of rutile. Relatively high density and birefringence can be distinguished from zircon.
Distribution of origin
The cassiterite deposit is closely related to the acidic granite magmatism. Among them, the cassiterite quartz vein and the cassiterite sulfur deposit are the most valuable. They are often symbiotic with fluorite, quartz, tourmaline and apatite, and are also concentrated in the sand mine. The main producers of cassiterite in the world are Malaysia, Bolivia, the United States, Germany, Australia, Namibia, Brazil and China. Gem-quality cassiterite is mainly produced in Bolivia. Tin mines are one of China's finest minerals. The most famous producing areas are Guangxi Dachang and Yunnan Gejiu, but few reach gem-quality.
In 1981, a columnar, 19.5-carat pale pink-transparent cassiterite crystal was found in the sand mine around the South China Tin Mine in China, indicating that China also contains such gem resources.
The reserves of sand and tin resources in the cassiterite resources account for about 15%. The main reason is the refractory high-iron residual sand and tin.
The reserves of the pulsed tin resources account for about 85%, of which about 85% of the primary vein tin ore is present in the polymetallic sulphide deposit. The cassiterite resources are mainly distributed in Malaysia, Indonesia, Thailand, the Philippines, Bolivia and other countries and regions.
application
Pure and transparent cassiterite crystals are attractive for their sparkle and dispersion. They are very fascinating gems. Only this high-quality cassiterite can be processed into a standard round diamond type faceted stone. It can also be used as a substitute for diamonds. Instead of colored diamonds, it is also easily confused with diamonds, brown zircons and vermiculite, but because of the high specific gravity and remarkable dichroism of the cassiterite, it is not difficult to distinguish it from the similar gems mentioned above. It is only this high-quality gem-quality cassiterite and its inlays that are rare to see at a high price. In addition to a small amount of cassiterite used to make gemstones and ornamental stones or collectibles, it is mainly used in industry. The tin content of cassiterite is as high as 78%, which is an important mineral for refining tin, which is more valuable than its gems. In the industry, tin can be used to make white iron, tin tubes, tin foil, various alloys and electroplating parts, and its oxides can be used to make dyes, enamels, porcelain and glass.
The most important raw material mineral for extracting tin. General industrial requirements (wB%): primary tin ore, cut-off grade Sn 0.1~0.2, industrial grade Sn 0.2~0.4; sand-tin mine, cut-off grade Sn 0.2, industrial grade Sn 0.4.
A fine crystal of tan to dark brown can be used as a gemstone.
The chemical composition of cassiterite is SnO2, and the crystal belongs to the tetragonal system of oxide minerals. It usually contains iron and finely dispersed inclusions of oxides such as lanthanum and cerium. Single crystals often have a double-cone short column shape, and also have a slender column shape or a double-cone shape. The knee-shaped double crystal is common, and the aggregate is mostly granular. Pure cassiterite is almost colorless, generally yellowish brown to dark brown, diamond shiny, broken grease luster, translucent to opaque, Mohs hardness 6.0-7.0, specific gravity 6.8-7.1.
The cassiterite is the most common tin mineral, mostly from the sand mine, and is the most important mineral raw material for tin smelting.
The cassiterite is mainly produced in the hydrothermal veins of granite intrusions or near rock masses, and is also often distributed in pegmatites and granites.
The world famous places are in Yunnan, Guangxi and Nanling, as well as Southeast Asia, Bolivia and Russia. China is one of the major countries producing tin in the world, and Guangxi Nandan Danda has the largest scale. Yunnan Gejiu Tin Mine has a long history of mining and is known as the “Sidu”.
[Introduction of the efficacy of tin mine]
Tin Mine ("Pharmaceutical Test")
[Source] is an oxide mineral cassiterite
[Mineral form] cassiterite ("Erya") tetragonal crystal, the crystal often has a double cone or a double cone and a square column, or a plate shape; and there are knee-shaped twin crystals, but usually in the form of scattered Granules or irregular grains appear.
The color is brown or black, and sometimes there are red, gray, white and other colors.
Streak is white or light brown
Diamond shiny or semi-metallic luster, resin gloss on the fracture surface, opaque
Unfinished
The fracture is semi-shell-shaped, or jagged
Hardness 6~7
Specific gravity 6.8 ~ 7.1
Mainly produced in gas-forming hydrothermal deposits
[Sexual taste] "Pharmaceutical test": toxic
[Indications - the efficacy of tin mines] "medicine test": grinding and bloated
Xiqiao dressing technology
The density of cassiterite is large, and it is re-elected as the traditional beneficiation process of cassiterite recovery. At the same time, the cassiterite is brittle and brittle, and the grinding process is easy to be pulverized. When the fine-grained inlaid cassiterite is recycled by re-election method, the tin recovery rate is low. The effective lower limit particle size of flotation is lower than that of heavy selection, which is one of the important methods for effective recovery of fine cassiterite.
The research status of the pre-mouth sillimanite beneficiation technology is summarized, and the research progress of the sulphur flotation agent, flotation new technology and cassiterite flotation mechanism are discussed. The cassiterite flotation collector mainly includes salicyloxyhepatic acid, styrene, oleic acid, etc.
The commonly used inhibitors are mainly water glass, sodium hexametaphosphate, methyl cellulose sodium and calcium lignosulfonate (GF). ), oxalic acid and other gangue inhibitors; flotation mechanism research mainly focuses on the flotation agent in the cassiterite and the adsorption mechanism, the adsorption form of the agent and minerals is mainly chemical adsorption; the new technology of cassiterite flotation mainly Electroflotation, carrier flotation, selective flocculation flotation, shear-flocculation flotation, dissolved gas flotation, and the like.
The research on flotation technology of fine-grained cassiterite unfolding system has important practical significance for improving the utilization rate of cassiterite resources, transforming the resource advantages of cassiterite into industrial advantages, and meeting the growing demand for tin resources in economic development. Broad application prospects.
It is difficult to obtain good tin sorting index and effectively recover other valuable metal components by single re-election method. Therefore, it is necessary to use physical ore dressing methods such as heavy, magnetic and electric, in combination with flotation, roasting, leaching and other chemical beneficiation methods to improve Recovery of tin and other valuable components in tin ore.
The sillimanite inlays in the Jianshipo sillimanite polymetallic sulphide ore in Jiangxi Province have fine grain size. Under the condition of 0.7% of the original ore Sn grade, the process of re-selecting tin by preferential desulfurization of floating zinc-flotation tailings is used to obtain Sn.
Grade 54.38%, recovery rate 54. 28% of tin concentrate and high quality zinc concentrate cassiterite brittle, easy to produce over-grinding phenomenon in grinding, bringing great difficulties to the cassiterite re-election process, easy to cause The loss of tin metal and the lower limit particle size of the effective flotation recovery are much finer.
Therefore, as a supplement to the re-election process, the fine-grained cassiterite which is difficult to recover can be re-selected by flotation treatment. In recent years, flotation has become one of the most effective methods for the recovery of fine cassiterite. According to the desulfurization-de-sludge-float-tin-tin concentrate re-sorting process, the Sn-grade sulphide of the Chehe Concentrator is 0.66%, and the tin with a Sn grade of 54% or more and a recovery rate of 54% or more can be obtained. Concentrate products.