# Kyanite

Kyanite, andalusite and sillimanite turn into heat-resistant mullite when fired, lining the furnaces that make steel, glass and cement.

Source page: https://www.materialinsights.org/commodities/kyanite/

Industrial minerals · No. 74

- Not on a critical list
 Industrial minerals · Foundation · Matter

Three minerals with the exact same formula turn into the heat-proof lining without which no steel furnace could run.

Chart: Illustration: Kyanite

##### Where it comes from

Chart: Map of where it comes from

These minerals form deep in metamorphic rock under different heat and pressure. Fired, they become mullite, which stays solid above 1,500 C.

##### Three things to know

1. Kyanite, andalusite and sillimanite share one formula, Al2SiO5, and become mullite when heated, holding shape above 1,500 C.
2. Ninety per cent of US kyanite-mullite output goes into refractories, and 60-70% of that is used by iron and steel.
3. The average value of US kyanite exports rose every year, from $369 per tonne in 2021 to $510 in 2025.

##### The journey

1. 1 **Metamorphic rock**Aluminous schist, gneiss or mineral sands
2. 2 **Open pit**Ore mined from surface workings
3. 3 **Concentrating**Flotation and magnetic separation
4. 4 **Calcining**Fired into stable high-alumina mullite
5. 5 **Refractories**Firebrick and castables for steel furnaces

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## Other sections

- [Overview](https://www.materialinsights.org/commodities/kyanite/overview/index.md)
- [Correlation](https://www.materialinsights.org/commodities/kyanite/correlation/index.md)
- [Extraction](https://www.materialinsights.org/commodities/kyanite/extraction/index.md)
- [Production](https://www.materialinsights.org/commodities/kyanite/production/index.md)
- [Stocks](https://www.materialinsights.org/commodities/kyanite/stocks/index.md)
- [Cycles](https://www.materialinsights.org/commodities/kyanite/cycles/index.md)
- [Trading](https://www.materialinsights.org/commodities/kyanite/trading/index.md)
- [Movement](https://www.materialinsights.org/commodities/kyanite/movement/index.md)
- [Criticality](https://www.materialinsights.org/commodities/kyanite/criticality/index.md)
- [Characteristics](https://www.materialinsights.org/commodities/kyanite/characteristics/index.md)
- [Emissions](https://www.materialinsights.org/commodities/kyanite/emissions/index.md)
- [Relationships](https://www.materialinsights.org/commodities/kyanite/links/index.md)