Overview
Crystal is a colorless and transparent quartz crystal of relatively pure composition. According to its nature and different uses, crystal is divided into four kinds of piezoelectric crystal, optical crystal, fused crystal and craft crystal. Although the main component of crystal and quartz sand, quartz sandstone, quartz rock is the same as SiO2, but because of the crystal has special electrical, optical, thermodynamic, process characteristics and higher SiO2 purity, so it is listed as a separate category of industrial raw materials. Usually there are two variants of quartz, one is a low-temperature variant, known as α quartz, a tripartite crystal system; the other is a high-temperature variant, known as β quartz, a hexagonal crystal system. The transition temperature of both at atmospheric pressure is 573℃. All the quartz seen in nature is alpha quartz. In the 1950s before the crystal is a strategic material. Because the natural crystal often contains a variety of inclusions, other minerals or color changes and it is difficult to meet the requirements of piezoelectric crystal and optical crystal, and therefore very few resources. 1960s, man-made crystals can replace the natural crystal. With the rapid development of electronics, communications, defense industry, the demand for ultra-high purity quartz is rapidly increasing, looking for alternatives to fused crystal has become a priority.
Two, mineral properties
Crystals are generally colorless and transparent, but natural crystals often contain traces of pigment ions, and show purple, yellow, smoke, tea, light rose, light green and other colors. Purple called amethyst, smoke yellow to dark brown called smoke crystal; light rose-colored called hibiscus stone, also known as rose quartz. Crystal crystals are hexagonal columns, crystal surface with transverse lines, usually crystal clusters or granular, massive aggregates, glassy luster, fracture shell-shaped and greasy luster, hardness of 7, density of 2.65 ~ 2.66g/cm3, with spinning and piezoelectricity.
Three, use
1) piezoelectric crystal can be used as a filter, resonator, used in electronic computers, a variety of automated weapons, aircraft, missiles, nuclear weapons, satellites, such as remote control, telemetry, electronics, electric parts and equipment.
2) Optical crystals are used in the manufacture of quartz refractometers, infrared analysis windows, spectrometers, spectrographs and so on.
3) Fused crystals are mainly used to manufacture a variety of quartz glass, optical fibers and their products, such as quartz crucibles, optical glass, quartz grids, chemical and medical vessels.
4) Craft crystals are mainly used as medium and low-grade gemstones.
Four, geological features
Based on the cause of crystal, surrounding rocks and other characteristics, crystal deposits are divided into five types.
1) Granite pegmatite-type crystal deposits. Pegmatite veins in groups produced in the fissure, swollen, irregular, lenticular, vein length of tens of meters to thousands of meters, a few meters wide to hundreds of meters; crystal endowed with granite pegmatite quartz nucleus, often for the huge quartz crystals, crystal defects are generally more in line with the industrial requirements of the lesser. *** raw minerals are fluorite, topaz, turquoise, feldspar, mica and rare metals. The industrial value of *** raw minerals is often greater than that of crystals. Inner Mongolia JiaoLiGeTai crystal deposit is an example.
2) wolframite-quartz vein crystal deposits. Wolframite is generally produced in quartz veins, the quartz veins containing wolframite are spread in a band. In the bifurcation of the quartz vein compound part, often form quartz crystal hole, crystal hole in the development of crystal huge crystal, some of which meet the industrial requirements. Hunan, Jiangxi, some tungsten ore associated with the quartz veins.
3) hydrothermal crystal deposits in granite. Granite body in the tensile fracture damage to the integrity of the rock body, by the late silicon-rich hydrothermal fluid filling, in the cross-compound or expansion of the formation of irregular crystal holes. Crystal ore is formed in the crystal holes. Granite often have garnet account phenomenon, sometimes forming rich ore. Hainan Island crystal deposits is an example.
4) hydrothermal crystal deposits in siliceous rocks. Crystal produced in siliceous rocks. Sometimes in the carbonate rock crystal hole can also form crystal ore, mineralized material from the nearby surrounding rock. The ore body is vein-like, vesicular, irregular or like layers, the crystal more comb-like structure. This type of deposit industrial significance. Jiangxi Lushan Luo Jia Shan crystal deposits is this type.
5) sand deposits. The above types of crystal deposits in the occurrence of weathering, other easy to weather the minerals are weathered, broken, and crystal is not easy to weather and remain in situ or in the vicinity of the formation of residual, slope or alluvial sand deposits. The size of the deposit is controlled by the intensity of weathering, some can form larger deposits, such as Jiangsu Donghai, Hainan Island crystal deposits.
Fifth, the distribution of deposits
China's crystal deposits, although most provinces and autonomous regions in the country have been found, but the resources are not rich. According to the Ministry of Land and Resources, in Guangdong, Hainan, Jiangxi, Jiangsu, Shandong, Shanxi, Shaanxi, Henan, Inner Mongolia, Xinjiang, Qinghai and other places have primary crystal ore and coastal crystal sand output. Can be used in high-tech fields of fused crystal and other high-purity silicon materials are in short supply, mainly by imports to solve.
Six, available resources
Smelting crystal and other high-purity silicon materials are aviation, aerospace, IT, military and other high-tech fields indispensable raw materials. The raw materials for the preparation of high-purity silicon materials are mainly high-quality natural crystals or highly purified natural quartz minerals. China's proven reserves of natural crystals less than a thousand tons, and can prepare high-purity silicon materials of natural quartz minerals have not been found in China. Some domestic organizations are also researching such raw materials, due to improper material, although after years of exploration, still can not make a breakthrough, and thus the preparation of high-purity silicon materials mainly rely on imports of raw materials. With the development of high-tech industry, China's demand for high-purity silicon materials is growing, from hundreds of tons in the 1990s, increased to about 1,400 t in 2004, the price of imports from 10,000 to 20,000 yuan per ton rose to 80,000 to 160,000 yuan. More importantly, these high-purity silicon materials are mainly controlled in the United States, France and other industrially developed countries in the hands of China's development of high technology and even economic security is very unfavorable. It is understood that the United States high-purity silicon materials, raw materials are mainly extracted from natural quartz minerals, after purification, the purity of up to 99.9965%, with an annual output of 2 × 104t or so. The United States to use its natural resources and advanced purification technology to control the global raw materials market of high-purity silicon materials.
China has similar mineralization geological conditions with the United States, looking for natural quartz minerals similar to the United States is entirely possible. Therefore, to carry out new resources of high-purity silicon materials to find mineral exploration and purification research, the development of the corresponding purification technology and equipment to ensure the safe supply of high-purity silicon materials is imminent.