KYANITE, ANDALUSITE AND SILLIMANITE

Economic deposits Kyanite, andalusite, and sillimanite make up the sillimanite minerals group. These naturally occuring minerals are polymorphic (Al2SiO5) but have differences in their respective physical, thermodynamic and crystalline structure properties. They generally occur as accessory minerals in rocks affected by high-grade regional or contact metamorphism. Stratiform replacement deposits also occur through alumina enrichment of silicarich metasedimentary and metavolcanic rocks by hydrothermal alteration. Sillimanite may occur within mineralized quartz veins and pegmatites. Additionally, these minerals may occur in paleo and modern heavymineral beach and stream placers. Economic and subeconomic concentrations of kyanite, andalusite and sillimanite occur in the Appalachian region of the Southeastern United States. Other known occurrences are in Alaska, California, Florida, Idaho, Nevada and New Mexico. Other economic occurrences outside of the United States include Australia, Brazil, Cameroon, Canada, China, Finland, France, India, Ireland, Kenya, Madagascar, Nigeria, Norway, Peru, Russia, South Africa, Spain, Ukraine and Zimbabwe. Industrial properties and uses The high alumina content, and thermal and volumetric stability of these minerals make them useful for high-heat-intensive refractory applications, metallurgy, investment casting molds, glass manufacturing and ceramics. High-quality specimens have a market for use as gemstones. Synthetic mullite (3Al2O3 · 2SiO2) and silica are produced through calcination of these minerals at temperatures ranging from 1,250 to 1,650 °C. Synthetic mullite has a melting point of about 1,840 °C, which contributes to highly resistant ceramic products. The majority of mined sillimanite group minerals are used in steel and iron manufacturing, so the production of iron and steel is a good proxy of global mineral production. A little less than a third of these minerals are used to produce ceramics, glass, nonferrous metals and cement. Other refractory uses include insulating brick, firebrick, refractory concrete, kiln furniture, mortar and gunning mix. Additional end products and uses include brake shoes and pads, abrasive products, electrical insulators, additives, fillers, and filtration of aluminum slag and impurities. Production and consumption The U.S. Geological Survey (USGS) estimates global production at 467 kt in 2023, lower than the previous 2018-2022 five-year average of 562 kt. The 2023 estimate included 170 kt of andalusite from South Africa, 100 kt of andalusite from China, 82.4 kt of kyanite and calcined kyanite from the United States, 65 kt of andalusite from France, 40 kt of andalusite from Peru, and 10 kt of combined sillimanite and kyanite from India (not including reclassified beach deposits). 2023 production totals are based on preliminary estimates by the USGS and data from the Virginia Department of Energy’s Mineral Mining Program. In Virginia, Kyanite Mining Corp. (KMC) is the largest producer of industrial-grade kyanite and mullite under the trademark names Virginia Kyanite and Virginia Mullite, respectively. KMC has operated surface mines and processing facilities since 1945 in Dillwyn, VA and produces a range of milled kyanite and calcined kyanite (more than 55 percent Al2O3, less than 0.85 percent Fe2O3) products that are shipped mainly by truck to domestic customers and to port facilities for delivery to international customers. Ore deposit geology consists of kyanite quartzite associated with a sequence of interlayered felsic and mafic metavolcanic strata of Ordovician age. Oregrade material contains 10 to 40 percent kyanite, averaging about 25 percent. In 2023, KMC reported production of approximately 82.4 kt of combined kyanite and mullite product. Annual production capacity at the Virginia operation is about 130 kt for commercial-grade kyanite concentrates and up to 39 kt for calcined kyanite per permit specifications and demand. Resco Products Inc. (Piedmont Minerals Division) has mined andalusite from an andalusitepyrophyllite (AlSi2O5(OH))-sericite deposit since 1958 to produce high-alumina firebrick and other specialty foundry and ceramic products in Hillsborough, NC. The USGS reports that two companies, based in Alabama and Georgia, produce synthetic mullite from a combination of feedstock materials such as kyanite, kaolin and bauxite. Additional details on production volumes were not available for the southeastern operations. Globally, South Africa, China, France and Peru produce most industrial-grade andalusite. Imerys Group is the leading producer, with operations in France and South Africa. Imerys Group has been mining in the Brittany region of France since 1970. The source of the andalusite near Glomel, France is highly weathered Ordovician-age schists adjacent to granitic rocks of the Armorican Massif. Imerys Group mines andalusite from the Rhino Mine in the Limpopo Province in South Africa. Mineral deposits are hosted in highly weathered pelitic rocks of the Pretoria Group associated with contact metamorphic rocks of the Bushveld Igneous Complex. Andalusite Resources (Pty) Ltd mined andalusite between 2001 and 2019 in the Thabazimbi area of South Africa. ARM Andalusite Resources (Pty) Ltd took ownership of the mine in 2022 and is currently focused on making improvements to the facility. Andalucita S.A. has been recovering andalusite since 2009 in northern Peru, with an estimated production capacity of 50 kt as of 2018. Xinjiang Xinrong Yilong Andalusite Co. Ltd, formerly known as Imerys Yilong Andalusite (Xinjiang) Co. Ltd, reported on its website that reserves of andalusite in China are estimated at 361 Gt. The website also stated that the company has an annual production capacity of 40 kt for andalusite products. India is the primary source for the global supply of sillimanite, with operations in the states of Maharashtra, Andhra Pradesh, Odisha and Kerala. Upward of 73 percent of the sillimanite resources occur in heavy-mineral-sand placers along India’s modern beaches. The Indian Ministry of Mines estimates total resources of more than 72.3 Mt of sillimanite, which includes approximately 8 Mt in proven reserves. The Ministry of Mines estimates total resources upward of 105.7 Mt of kyanite, with 393 kt in proven reserves. Foreign trade and prices The ore grade and purity, quantity, particle (mesh) size, packaging, monetary exchange rates, source and destination influence annual import and export prices for mineral commodities. In 2023, the U.S. Census Bureau reported global exports of approximately 43 kt of kyanite and 26 kt of mullite. Kyanite was valued at $428/t and mullite at $501/t. According to the U.S. Census Bureau, imports of sillimanite minerals to the United States were estimated at 5 kt in 2023. Trends and outlook Refractory uses of these minerals are important for the global steelmaking industry; therefore, trends in steel production are associated with the market demand for the sillimanite minerals group. The World Steel Association estimated global steel production at 1,892 Mt in 2023. China leads in total steel production (1,018 Mt), comprising 54 percent of the global output for 2023. India (second), Japan (third), the United States (fourth) and Russia (fifth) round out the top five producers. Steel production in the EU, with a 2019-2023 five-year average of 142 Mt, was down 15 percent from the 167 Mt of the previous five years (2014-2018). The United States will likely continue to see an increased demand for steel as a result of increased electric-vehicle manufacturing and available funds from the Infrastructure Investment and Jobs Act to spur new construction and improvement projects. Demand for raw materials associated with steel production is likely to continue to occur globally; however, effects from the COVID-19 pandemic, supply-chain disruptions and the ongoing Russia- Ukraine war may influence the scale of growth, particularly in European markets. References Andalusite Resources, 2024 Andalucita S.A., 2024 Government of India, Ministry of Mines, Annual Report 2022-2023 Hatfield, A.K., 2024, Kyanite and Related Minerals: United States Geological Survey, Mineral Commodity Summaries, January 2024 Hatfield, A.K., 2022, Kyanite and Related Minerals: United States Geological Survey, Minerals Yearbook 2022 Tables, October 2023 Hatfield, A.K., 2019, Kyanite and Related Minerals: United States Geological Survey, Minerals Yearbook 2019, March 2024 Imerys, 2024 Indian Bureau of Mines, Ministry of Mines, Government of India, Indian Minerals Yearbook 2022, Part 1: General Reviews, Production KMC, 2024 - Kyanite Mining Corporation Resco Products, Inc., 2024 US Census Bureau, 2024, USA Trade Online Virginia Energy, 2024 - Virginia Department of Energy, Mineral Mining Program 2023 Annual Production Data World Steel Association, 2024

KYANITE, ANDALUSITE AND SILLIMANITE

Authored by:
David W. Hawkins

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