What is quartz
Quartz or silica is a very common mineral in our daily life. Its composition is SiO2. The single crystal of SiO2 is crystal, while the polycrystal forms chalcedony and agate. The ordinary glass we usually see is SiO2 without crystal structure. The sand on the beach is basically composed of quartz and feldspar.
Everyone should be familiar with quartz. However, in recent years, with the rise of quartz stock prices, the quartz market has changed and set off a “high-purity quartz sand craze”.
What is high purity quartz? What is the difference between it and our common quartz? What kind of quartz can be used to make chips?
What is high purity quartz
High-purity quartz refers to quartz and its products with extremely high purity of SiO2 and extremely low content of impurity elements, which are widely used in semiconductor, photovoltaic, optical fiber, precision optics, advanced lighting equipment, new glass and other industries.
However, because different industries require different qualities of quartz, there is no universal quality evaluation index for high-purity quartz. Different people have different definitions.
Early studies believed that the impurity content of high-purity quartz should be less than 50×10-6, that is, quartz with SiO2 purity greater than 99.995% is high-purity quartz. The Norwegian Geological Survey proposed more detailed indicators, requiring not only the total mass of impurities to be less than 5/100,000, but also the content of Al to be less than 3/100,000, the content of Ti to be less than 1/100,000, Na and K The content of Li and Ca should be less than 5ppm, the content of Fe should be less than 3ppm, the content of P should be less than 2ppm, and the content of B should be less than millionth.
In 2014, Flook put forward a new quality index according to the needs of the market industry. It believed that quartz with a purity of SiO2 of 99.95% and a total impurity content of less than 5/10,000 was high-purity quartz, and quartz with a purity of 99.5%~99.8% could meet the requirements of semiconductors. According to the requirements of filler, optical fiber, and liquid crystal screen production industries, quartz with a purity of less than 99.5% can be used in the transparent glass industry.
Quartz is often doped with trace impurities in the process of natural crystallization, mainly gangue minerals, inclusions, and lattice impurities in the crystal gap. Like the river sand and natural sand we usually see, there are too many impurities. The silicon content of river sand is generally 65%~85%, and the silicon content is too low to be used in the production of chips. The type and content of impurity elements will affect the performance of quartz. For example, the presence of Al will affect the light transmission rate in quartz. Metal elements such as Fe and Mn will reduce the light transmittance of quartz. Quartz with too high P and B content It cannot be used in the photovoltaic industry, so when producing high-purity quartz, the raw ore must be purified to reduce Al, K, Na, Li, Ca, Mg, Fe, Mn, Cu, Cr, Ni, B, P, etc. content of impurities.
Compared with ordinary glass, ultra-white glass is crystal clear, has high light transmittance, and has extremely low iron content (Fe2O3 mass fraction does not exceed 150×10-6), it is only one tenth of that of ordinary glass, or even lower. When the iron content exceeds the standard, the glass not only loses its transparency, but the finished product will also appear yellow-green. And ultra-white glass is safer, its self-explosion rate is only about 1/10,000, which is much lower than ordinary glass (the self-explosion rate is about 3/1,000), and it is especially suitable for the construction of important buildings and high-rise buildings. Therefore, in terms of impurity element content and silicon content requirements, the new glass industry and semiconductor industry will have stricter requirements.
Strictly speaking, high-purity quartz is not a mineral, but a product purified from crystal, vein quartz, quartzite, granite pegmatite and other ores as raw materials. This kind of high-purity quartz sand does not exist in nature, and it needs to be mined and purified from quartz ore before it can be used in semiconductor manufacturing. Therefore, the ore deposit that can be purified to produce high-purity quartz is called high-purity quartz raw material ore. The most ideal choice for preparing high-purity quartz sand is high-purity quartz ore raw material. Quartz or quartz veins are very common, but high-purity quartz ore, especially high-purity quartz ore with economic mining value, is very rare.
High purity quartz source worldwide
High-purity quartz sand is an indispensable raw material for computer chip manufacturing and the material basis for high-end products in the silicon industry, and high-purity quartz raw materials are extremely scarce. At present, high-purity quartz raw material deposits are mainly distributed in 7 countries including the United States, Norway, Australia, Russia, Mauritania, China, and Canada.
According to the statistics of the United States Geological Survey, as of the end of 2019, the global high-purity quartz raw material mineral resources are about 73 million tons, of which Brazil is the country with the largest resource volume in the world, with a resource volume of 21.11 million tons, and the ore type is mainly natural crystal. The United States is the country with the second largest resource volume, with a resource volume of 18.22 million tons, and the ore type is mainly granite pegmatite quartz. Canada ranks third in the world, with resources of 10 million tons, and the ore type is mainly vein quartz.
The Spruce Pine Mine in the United States has the largest annual output of high-purity quartz raw materials, exceeding 10 million tons. The smallest annual output is Norway’s Drag Mine, which is only 267,000 tons.
USA
Spruce Pine Mine
The Spruce Pine high-purity quartz raw material mine is located in Spruce Pine, Mitchell County, western North Carolina, USA. The mining area has a long mining history of more than 100 years. The content of impurity elements in quartz is extremely low. After mechanical and chemical purification, high-purity and ultra-pure quartz are mainly used in semiconductor crystals, precision optical glass, photovoltaics, lighting and other industries. The mine supplies more than 90% of the world’s demand for high-purity quartz sand, and it is even the only source for a long time. In 2009, the BBC called it “the most strategic square acre on earth”. (Nelson, 2009)
Until August 2020, the mining rights of the deposit were acquired by Norway’s The Quartz Corp. , TQC and Sibelco North America, Inc., a wholly owned subsidiary of Sibelco in Belgium. Holding, mining of quartz, feldspar, mica in white granite and pegmatite.
TQC is a joint venture between Norwegian Crystallites AS and K-T Feldspar Corp. of Spruce Pine. , The Feldspar Corp. Merged in 2011, it is responsible for crushing, sorting and primary flotation of the mined ore locally, and then shipping the semi-finished product to the deep processing plant in Norway, after secondary flotation, magnetic separation, acid leaching, and high-temperature roasting , to produce a product with a quality similar to Sibelco’s high-purity quartz sand.
Bovill Mine
The Bovill Mine is located in Bovill, Latah County, northern Idaho. According to electron probe analysis, the purity of quartz crystals in the ore is greater than 99.9%. In 2010, I-Minerals, Inc. completed the pre-feasibility study and developed a high-purity quartz sand product with a SiO2 purity of 99.9%~99.997%. The proven resources of potassium feldspar and quartz in the deposit are 4.378 million tons, and the controlled resources are 8.857 million tons, totaling 13.235 million tons (I-Minerals, 2020a). Boville Mine has huge resources of high-purity quartz, and the ore purification process is relatively difficult. Using the traditional flotation purification process, high-purity quartz sand can be produced.
Australia
Australia is rich in quartz resources, mainly distributed in northern Queensland, Victoria and Western Australia. Among them, northern Queensland is the main source of high-purity quartz raw materials, and many deposits such as Lighthouse, Sugarbag Hill, White Springs, and Quartz Hill have been discovered so far.
Lighthouse
The deposit is located at Georgetown in northern Queensland. The town of Einasleigh is 16km southwest of the mining area and is the nearest town. The lighthouse deposit is composed of two quartz peaks in the east and west that look like lighthouses and are about 440m above the surface, hence the name. The ore in this mining area is pure, translucent or milky white, massive, and filled in faults in a nearly vertical shape. After testing, the ore purity of the east and west ore bodies is >99.9%, and the main impurity elements Al, Ti, Fe, P, Ca, etc. are all low. After simple mechanical purification, the purity can reach more than 99.95%, which proves that the Dengta deposit is High-quality high-purity quartz raw material ore.
Sugarbag Hill
The deposit is located in Georgetown, about 25km from Georgetown in the northwest and 60km from the Lighthouse Mine in the east. The ore quality is extremely high-quality, and the in-situ SiO2 purity can reach more than 99.99%. The 2016 census results show that the ore body is about 600m long and has an average thickness of 20m, and the depth of the ore body revealed by drilling is 60-80m (Alper, 2019). After sampling tests and ore dressing and purification experiments, the purity of high-purity quartz sand can reach 99.995%~99.999%, which meets the quality requirements of the solar energy and semiconductor industries. At present, the Tangdaishan deposit has not been mined and produced high-purity quartz sand, but its proven and controlled resources are considerable and can be mined in the open pit.
White Springs and Quartz Hill
The White Springs and Quartz Hill mines are located along Highway 1 from Georgetown to Mt.Surprise. The deposits are all keatite vein type. The ore quality of the White Springs Mine is excellent, and the purity of raw material SiO2 is over 99.99%. It is inferred that the resources of high-purity quartz are 1.5 million tons. The purity of Quartz Hill’s raw materials is greater than 99.5%, and the estimated high-purity quartz resources are 14 million tons, with a huge resource scale. The purity of high-purity quartz sand produced by White Springs Mine covers 99.99%~99.999%, with an annual output of 30,000 tons of high-purity quartz sand, which is used in the photovoltaic and semiconductor industries. Currently, the Quartz Hill deposit has not yet entered the mining period.
Creswick
The deposit is located at Creswick in south central Victoria. The deposit is of the gold mine tailings type, consisting of abandoned tailings from gold mines mined during the gold rush in the 19th century (Hughes, 2013). The ore is 6-200mm quartz gravel in tailings, with excellent quality and low content of impurity elements, especially B and P, which can be used in liquid crystal display, photovoltaic, semiconductor, optical glass and other industries. After being treated by the Australian Commonwealth Scientific and Industrial Research Organization (CSIRO) using traditional mechanical and chemical purification processes, the purity of high-purity quartz sand SiO2 can reach 99.995%.
Russia
On the east side of the Ural Mountains in Russia, there are two high-purity quartz deposits, namely the Saranpaul deposit in the subpolar Urals and the Kyshtym deposit in the South Urals. Among them, the Keshtem Mine has a large scale and a high degree of development, and its high-purity quartz products are of high quality.
Kyshtym
The Shtym deposit is located in Kyshtym, Chelyabinsk, Russia, 100km southeast of Chelyabinsk. The deposit is of hydrothermal vein quartz type. The total length of the mining area is 15km, the width is 1-3km, the area is 20km2, and the quartz reserves are 1.36 million tons. The development of ore deposits began in the 1960s and 1970s, and it has been more than 50 years. Early mining was mainly used in traditional industries such as building materials and glass. After 2011, mining and production of high-purity quartz sand began. The production capacity is 6,000 tons per year in 2022, and the mine can meet the 30-year service life of full-load production.
Saranpaul
The Saranpaul deposit is located in the northwest edge of the Berezovsky District in the Khanty-Mansi Autonomous Okrug-Ugra of Russia, 85km southeast of the Saranpaul village . The deposit is of hydrothermal vein quartz type. The ore is translucent-transparent, with glass luster. According to the exploration report of the mining area in 2014, the resources that can be used as high-purity quartz are 330,000 tons (Development Corporation JSC, 2017). In addition, many unexplored quartz veins have been found outside the mining area, and the amount of prospective resources may be even more impressive.
Mauritania
Umm Agueina
The deposit is located in Nouadhibou Province (Dakhlet Nouadhibou) in the west of Mauritania, 130km west of Nouadhibou port. The deposit is of hydrothermal vein quartz type. The ore is light gray translucent, smooth and transparent, and the SiO2 content of some sampled ores is greater than 99.8%. Orebodies exposed at the surface appear as broken large veined quartz gravels overlaid with a small amount of laterite. The inferred resources of quartz are 5-10 million tons (Feytis, 2010), but due to the lack of drilling verification, test analysis and necessary mineral processing experiments, the resources that can be used as high-purity quartz raw materials are unknown. As of now there is no active mining activity.
Chami
The Chami deposit is located in the east of Dakhlet Nouadhibou Province, 20km away from the Umm Aquinina mine. The genesis, ore type, surrounding rock, and occurrence characteristics of the deposit are similar to those of the Umm Aquinina Mine. The ore is translucent, smooth and transparent, and the SiO2 content of the ore is 98% to 99.9%. The proven reserves of high-purity quartz raw materials above 2.7m in the surface layer are 725,000 tons; the ore bodies below 2.7m can be extended to 8m, and the proven reserves have room for further expansion.
Canada
Johan-Beetz
In the coastal zone of Johan Beetz Bay in southeastern Quebec, Canada, 10 northeast-southwest trending hydrothermal vein quartz ore bodies are exposed on the surface, namely John Beetz high-purity quartz raw material ore. The results show that the SiO2 content of the ore is 98.7%~99.6%, and the average content of impurity elements B and P are lower than 0.25×10-6 and 0.2×10-6 respectively, which can be used to produce photovoltaic quartz crucibles. After accounting for mining losses, the controlled high-purity quartz resources of the surface ore bodies of Vein 2 and Vein 9 are 1.743 million tons and 507,000 tons, respectively, totaling 2.25 million tons (Bathalon, 2014).
Norway
As a long and narrow mountainous country from north to south, Norway is rich in quartz resources and has global quartz industry giants such as TQC and Elkem ASA. Based on the test data of quartz ore in the country, the Norwegian Geological Survey also proposed a set of high-purity quartz quality evaluation indicators based on the content of lattice impurity elements (Müller et al., 2007; Müller et al., 2012). Currently, the Drag deposit in the north and the Nesodden deposit in the south are the main sources of high-purity quartz raw materials in Norway.
Drag
The Drag mining area is located near the village of Drag on the west side of Tysfjord, Nordland County, Northern Norway. It consists of dozens of pegmatite-type quartz ore bodies distributed in a radius of 5km2. composition. Quartz crystals are pure, with an average particle size of 6 mm, and lattice impurity elements such as Al, Ti, Li, and B all meet the quality requirements of high-purity quartz raw materials (Müller et al, 2012). Mining at the Drag Mine began in 1907. The early mines mined the potassium feldspar in the pegmatite in the open pit, and in 1996 began to mine and produce high-purity quartz sand for optics, lighting equipment, and photovoltaics.
Nesodden
Nesodden is located in Kvinnherad, Hordaland County, southwest Norway. The ore body is about 580m long, 15m wide, and extends 150m. The quartz crystals in the ore are relatively large. As of now, the Nesodeng high-purity quartz mine has not been mined. However, the mine has considerable influence on the high-purity quartz sand and products industry. The resources of the deposit are large and the backup resources of high-purity quartz in the mining area are quite rich. In the northern section of the fault zone, Kvalvik (Kvalvik) hydrothermal vein quartz ore was also discovered, with an inferred resource of 700,000 tons. The ore quality is similar to that of Nesodden Mine, which can be used as high-purity quartz raw material.
China
LinQiuShan
LinQiuShan Quartz Mine is located in Hengche Town, about 20km northwest of Qichun County, Hubei Province. Drilling sampling analysis results show that the ore is almost entirely composed of quartz, with a crystal grain size of 1-2mm. Ore SiO2 purity> 99.35%, Al2O3<0.22%, Fe2O3<0.02%. At present, LinQiuShan Quartz Mine adopts open-pit mining, and its designed mine scale is 15,000 tons of ore per year.
