Kyanite is a polymorphic aluminum-silicate mineral that has the same chemical formula as the minerals andalusite and sillimanite, Al₂SiO₅ (sillimanite minerals group). The atomic structures of these minerals differ slightly as do other physical properties. Mullite is a closely related mineral with the chemical formula Al₆Si₂O₁₃ that occurs rarely in nature, but can be synthesized from kyanite and other alumina- and silica-enriched minerals using a thermal treatment process referred to as calcination. Kyanite is valued as an industrial raw material for the manufacture of heat and acid refractories used in ceramics, precision castings, refractory additives and fillers, and other applications in the ferrous and non-ferrous foundry industries. Due to the qualities of hardness and durability, exceptional specimens of the sillimanite minerals group are often marketed in the gemstone and jewelry industry.

Kyanite and the other sillimanite minerals are common constituents in metamorphic rocks, often making up a percent or two of the mineral composition of peraluminous gneisses and schists in the Piedmont geologic province of Virginia. Economic deposits are found in a variety of geologic settings that include massive segregations in metamorphosed aluminous sediments, as stratiform replacements within foliated and nonfoliated quartzose rocks often associated with meta-volcanic strata, mineralized quartz veins and pegmatites, and in residual soils and placers.

The largest producer of industrial grade kyanite is Kyanite Mining Corporation (KMC), which has operated surface mines and processing facilities since 1945 in central Virginia. Active mining occurs at two locations (Willis Mountain and East Ridge), where the ore deposit geology consists of kyanite quartzite associated with a sequence of interlayered felsic and mafic metavolcanic strata of Ordovician age. The kyanite ore [DH2.1][DH2.2]generally makes up 10-40 percent of the host quartzite rock. The company markets a range of milled kyanite and mullite products that are shipped mainly by truck to domestic customers and to port facilities for delivery to international customers. The company reports an annual production capacity up to 143,000 tons of commercial grade kyanite and 43,000 tons of calcined kyanite (2023).

 

Year of first production in Virginia: 1920s
County locations with commercial mining (past and present): Prince Edward, Buckingham
Quantity produced in 2025: 89.5 thousand tons
Estimated value of produced minerals in 2025: $41.0 million

Additional information on global resources and production of kyanite and other sillimanite minerals may be found in the 2026 annual industrial minerals review article in Mining Engineering, a monthly periodical published by the Society for Mining, Metallurgy and Exploration, Inc., (SME), typically published in July