Kyanite is a member of the sillimanite group of minerals. This mineralogical group includes kyanite, andalusite, and sillimanite – all of which are naturally occurring polymorphs of Al2O3.SiO2. These minerals are also commonly referred to as the 1:1 “alumino-silicates”.

Despite their similarities, each of these minerals has a unique crystalline structure, and it is these differing crystal structures that give each compound its distinct physical properties. Many of these differences work in favour of kyanite as a raw material additive for refractory and ceramic bodies.

Key Properties

Kyanite, which occurs in nature is an elongated, “lath-like” crystals, has many important (and several unique) properties that make it a valuable raw material in refractory and ceramic products. Kyanite contains 60% alumina – which means that it is a relative cheap source of refractoriness. It also decomposes into a high hot strength phase mullite at a relatively low temperature (1325°C), thereby inducing faster sintering. But most importantly, it undergoes a large and irreversible expansion at this temperature – and it is this expansion that is used by many refractory and ceramic manufacturers to reduce shrinkage during initial firing.

In addition, the “lath-like” habit of the kyanite crystal lends cold “green” strength and abrasion resistance to products that are made from it.


Source: Kyanite Mining Corporation

For more information on this source please visit Kyanite Mining Corporation.



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