some 150 years ago.
Andalusite occurs as prismatic crystals or as granular masses often as a constituent of metamorphic rocks. It comes in pink, green, yellow, violet, pearl gray, purple red colours among others. It is orthorhombic in crystalline form, has moderately high refractive indices, weak birefringence, negative elongation, optically negative sign, and large optic angle. Specific gravity of andalusite varies from 3.15 - 3.20 and hardness of 7.5 in Moh’s scale. When heated above 1410OC, Andalusite converts to Mullite with free Cristobalite practically without any volume change and so, a negligible change in specific gravity. (Because of this and a few more properties, andalusite finds application as a raw material in refractory industry).
crystals of andalusite up to 7 cm long have been found in Kabardino-Balkaria in Russia, along the Baxan River. In the Urals, multi-coloured andalusite crystal deposits were extracted at the Svetlinskoye deposit; and in the Ilmeny Mountains their size in pegmatites reached 20-60 cm.
However, andalusite is mostly available in France (Kerphalite), Spain, South Africa (Durandal, Krugerite, Purusite, Randalusite) and China (Yilongite). In fact, South Africa has the world’s largest reserves of andalusite and the Maroeloesfontein Andalusite Deposits in the Thabazimbi region is rife with this rich mineral. Typical Chemical Composition of South African andalusite deposits (Randalusite, Krugerrite, Prusite) are shown in the table below.
Both andalusite industry and andalusite market are dominated by just a few companies who produce majority of andalusite for the global market. The South African Mineral Resource Committee (SAMREC) and Denain-Anzin Mineraux Refractarie Ceramique (DAMREC), the South African and French divisions of the industrial minerals conglomerate, IMERYS namely, Rhino Minerals Pty Ltd (IMERYS), Samrec Pty ltd (IMERYS), Damrec (IMERYS), Picobello Andalucita and Andalucita S.A. dominate worldwide andalusite production. Damrec, subsidiary of IMERYS, is the largest producer of Andalusite and has operations in China, South Africa, France and Peru. In March 2002, a new South African company, Andalusite Resources started to build its greenfield site and started commercial production in the second quarter of 2003. Andalusite Resources is doing major mining and beneficiation operations in the Northern Transvaal. A year ago Andalusite Resources had the capacity to produce 50,000 tonnes per annum with operations at 4,000 tonnes per month. Now it has ramped up to 6,000 tonnes per month with goals of producing 6,500 per month and 80,000 tonnes annually.
Andalusite occurs in argillaceous and micaceous slates, in schists and gneisses, and as crystals resulting from the contact metamorphism of intrusive rocks.
Except for small amounts here and there, there is no big deposit of andalusite in Indian subcontinent. The gem-quality andalusite is also extracted from the placers. Veins with
Andalusite (mixed with prophyllite) is also produced by Piedmont Minerals Company, an American company based in Hillsborough, North Carolina, and in small amounts by various producers in India and China mainly for domestic uses.
The andalusite industry is driven by the growth of refractory industry, which depends heavily on one of its main end users - the steel industry. The continued demand for andalusite by China for its refractory industry is expected to drive the demand of andalusite. Although its end users other than the steel industry consume less andalusite yet, they have a strong impact on the growth of andalusite industry. Some other industries like - ceramic, glass, aluminium and cement etc. together also contribute to the growth of andalusite industry.
While an increasing trend of steel consumption and production indicates a sound prospect for andalusite industry but on the other hand, steel companies becoming technically more efficient and cost conscious, making strides to consume minimum refractory per ton of steel production could be a reason of anxiety for andalusite market in future.
According to a rough estimate the andalusite market at present is around 400000 tonnes worldwide. The andalusite industry has good reasons to be optimistic since the emerging markets like China, India, Russia with heavy refractory consumption, that were using till recently bauxite-based refractories where andalusite-based refractories could work, have now started realise the advantage of andalusite-based refractories over the former. The depletion of refractory grade bauxite in India and the non-availability of low-cost Chinese bauxite for export are some other reasons of growing andalusite industry.