Supply Situation Report: Mullite

By Mike O'Driscoll
Published: Monday, 23 August 2010

Supply, demand and consumption trends in the mullite industry


All mullite production is synthetic, either by sintering or fusing aluminosilicate raw material feedstock. Mullite’s two main inputs can be identified as aluminosilicate minerals and energy. Proximity to supply of at least one or both of these inputs is a prerequisite for most mullite producers.

The supply sector for mullite is a widely dispersed but relatively select group (see map), concentrated in the USA, Brazil, Europe (UK, Germany, Hungary), China, India, and Japan.

With the exception of C-E Minerals, USA, and a few Chinese producers, most sintered production units are <20,000 tpa, while fused mullite units are <10,000 tpa.

It is worth noting that significant mullite production capacity comes under Imerys in the USA (C-E Minerals, Georgia), Germany (Treibacher Schleifmittel Zschornewitz GmbH), and Brazil (Treibacher Schleifmittel Brazil Ltda).

C-E Minerals is the market leader with by far the largest capacity (estimated total production capacity of 700,000 s.tons) and well established Mulcoa grades, the specifications of which are often recognised as benchmarks by many other producers as well as consumers.

C-E Minerals does not monopolise the sintered mullite market, but it would be fair to say it dominates this sector. As a result, there have been and will continue to be many suitors emerging to rival C-E Minerals’ grades, naturally with a view to under cutting prices and attempting to grab a slice of the market. Some have been moderately successful on a limited scale, many others have failed.

Naturally, when there is any slight bottleneck or hiccup in supply from the USA, then alternative players strive to make the most of the opportunity.


The primary market for mullite is in refractories, although ceramics and foundry markets are also important consumers.

With steel recovery continuing and many refractory customers seeking alternative aluminosilicate refractory minerals to refractory bauxite, mullite has certainly been receiving increasing interest recently.

Indeed, industry sources in the USA, Europe, and South East Asia have expressed concern over constraints in supply of 60% Al2O3 mullite grades from the USA. One speculative reason suggested that this shortage was in part owing to production problems in late 2009/early 2010 at C-E Minerals.

Melvyn Bradley, technical manager, Minelco Ltd, UK said: “This shortage, along with the drive [by consumers] to reduce costs, has seen renewed interest in mullite 60 and 70 grades out of China.”

On the other hand, as with many other Chinese mineral exports, Chinese mullite prices are rising and future availability is uncertain. “An opportunity lost for C-E, especially at a time when China is upping the prices of its exported raw materials. The need for alternative supplies of refractory raw materials outside of China is increasing” considers Martin Burke, formerly operations manager at Eco Refractory Products, Malaysia.

C-E Minerals certainly acknowledges the upturn in demand, but insists that it has responded to the market. The company restarted all its kilns at Andersonville, Georgia, in Q4 2009, and in Q1 2010 brought on stream a new kiln which has added 75,000 tpa to the company’s existing capacity.

Mike Pierce, vice president-sales, C-E Minerals told IM: “Global demand for refractory products surged in Q4 2009 and H1 2010 as a result of the recovery of steel production and the sharp reductions of refractory inventory implemented in 2009 across the supply chain. Sales volumes across C-E Minerals’ product lines were up by 60% to 90% in H1 2010.”

“While we were implementing these initiatives, lead times for delivery of certain products increased in the first months of the year. They are now getting back to normal.” Pierce added.

The other sintered mullite producer in the USA is Kyanite Mining Corp. (KMC) which calcines kyanite to obtain its Virginia Mullite grade. KMC admits that it has a limited range of particle sizes with its natural grade, whereas synthetic mullites do not face such particle size issues, since they are manufactured by extruding blends, firing, and then sizing.

Hank Jamieson, vice president, director of sales and marketing, KMC, commented to IM: “Although the demand for our Virginia Mullite has picked up nicely since the depths of the recent recession, KMC has room to grow our mullite business without bumping up against capacity constraints. Using a natural mullite has its benefits, which now includes availability.”

While there is a range of Chinese mullites on offer, in recent years they appear to have rarely troubled C-E Minerals’ market share to any great extent.

China Mineral Processing Ltd, based in Tianjin, China produces its Reframul (RM) sintered mullite grades through Shanxi Diversified Industrial Corp. in Taiyuan, and Jie Xiu Bauxite Plant, both in Shanxi.

A CMP spokesperson said: “None of the Chinese products directly substitute Mulcoa, but strangely, because the RM70 from China is harder than Mulcoa, it is finding more of a market as a bauxite replacement”

Zhengzhou Zhixing Mineral Co. Ltd, China, produces 5,000 tpa fused mullite and 8,000 tpa sintered mullite. Sunny Gao, general manager, Zhengzhou Zhixing reported to IM:“Including the demand in China, our mullite is being exported overseas with increasing volume each month.”

One ramification of the predicament of speciality aluminas producer Almatis GmbH (see p.10) has been a reported lack of supply of certain of its grades. This has impacted prices (see below) and prompted consumers and traders to secure alternatives.

An industry trader remarked to IM: “Lower grades of bauxite from China are now being marketed as mullite; the problem is in the SiO2 % and hardness.”

In Germany, Nabaltec AG produces high purity speciality sintered mullite grades under the SYMULOX¨ brand with minimum 72% Al2O3, and mullite phase 90%. Markets include glassmaking, incinerator linings, and kiln furniture.

Jan Kupfer, director Business Division Technical Ceramics, Nabaltec said: “We have seen increasing demand beginning from Q2 of 2010 owing to a revival of investment activities in different industries. A further increase in demand is expected for the near future as order volumes continue to rise moderately.”


Sintered mullite grades are usually priced in accordance with their alumina content, which ranges from the lower grades of 47% and 50% Al2O3, to the higher ranges of 60% and 70% Al2O3. Prices may range $198-600/tonne FOB USA.

With the perceived shortage of alumina grades from Almatis, an industry trader told IM: “There is a lot of upward price pressure and lack of supply in their [Almatis] product range, which is knocking on to brown fused alumina and bauxite. Both are moving up and that’s dragging up Chinese 60 and 70 mullite [prices], at the same time Mulcoa prices are going up as well, as are freight rates, especially containers.”

Chinese FOBT sintered mullite prices have been quoted as: 60% Al2O3, $400/tonne; 70% Al2O3, $425/tonne; and 47% Al2O3, $285/tonne.

The world of mullite: locations of leading sintered (s) and fused (f) mullite producers*

*for full company names and details see table in IM February 2010, p.43, “Sillimanite supply surge”

Mullite basics

Mullite (3Al2O3-2SiO2) is a mineral phase named from one locality on the Isle of Mull, Scotland, where argillaceous sediments have been fused by igneous intrusion.

Natural mullite occurrences are rare and uneconomic to mine, thus all commercially produced mullite is synthetic, ie. produced by either sintering or fusing selected aluminosilicate raw materials.

Such feedstock materials for sintered mullite include: kyanite, bauxitic kaolin, and for higher purity grades, carefully selected blends of alumina, kaolin, and bauxite.

Fused mullite grades can be produced from fusing Bayer process alumina and high purity silica, or by fusing certain blends of bauxite, aluminas, and refractory kaolins. Zirconia can also be added.

Mullite has a melting point of 1,810¡C, and a specific gravity of 3.156. Commercial sintered mullite grade categories are 45-50%, 60%, and 70+% Al2O3. Other important properties are low iron (<1% Fe2O3) and low cristobalite, and a mullite phase ranging 65-90%.

Mullites show a uniform rate of thermal expansion and are resistant to spalling and deformation under load. Their strength is due to the interlocking of long, needle-like crystals.

Sintered and fused mullites are used in the refractories, ceramics, foundry, and investment casting markets.

Specific uses


Steel: blast furnace hearths, metallurgical crucibles, well blocks and ladle nozzles, sliding gate plates.

Glass: hot repair burner blocks, crowns of fibreglass furnaces, fore hearth, expendables, chequers.

high tech. kiln furniture, hot zone and car top decks of tunnel kilns, rollers for roller kilns

Investment casting:
stuccos, slurry coats

mullite porcelains are used in spark plugs and laboratory ware; fused zirconia mullite is used in speciality product applications where a high resistance to environmental corrosion and a low coefficient of thermal expansion are desirable properties, eg. ceramic pressure casting tubes, setters and saggers, and refractory shapes requiring resistance to molten slag and molten glass.

Togni to double capacity by 2012

Brazil’s refractories, sintered mullite, and kyanite producer, Togni SA, is celebrating 100 years in the business. Livio Togni, operation vice president, talked with IM about Togni’s plans for the future

Anibal Togni, president (left), and Livio Togni,
operation vice-president.

Togni SA has been active in Popos de Caldas, Minas Gerais, Brazil since 1910. Originally, the company manufactured building bricks and roof tiles, but in 1954 started production of refractory materials pioneering the use of local clays.

With two plants in Popos de Caldas and one in Sacramento, Minas Gerais, the company produces 60,000 tpa refractories for a range of markets.

Summarise Togni’s primary activities.

We are mining and processing kyanite mostly for our own consumption (we do sell some to the local market). Because the majority of Brazilian clays for chamotte production are high in alumina, the use of kyanite for shrinkage compensation is very little, so the main usage of kyanite is for “in situ” mullite formation in the matrix of refractories (mainly monolithics). For this application the product should be unfired and in fine particles.

The use of calcined grades are seldom used, because if you compare with fused mullite (mostly preferred) the physical properties are quite different. We produce close to 1,000 tpa of kyanite and we have reserves of approximately 2m. tonnes.

What recent investments has Togni implemented?

Plant No.1 has received a new milling system, a new section of hydraulic presses and we are in the process of installing a new weighing and mixing system, and plan a new tunnel kiln to be built in the next year or two.

Plant No.2 has received a briquetting facility and a new rotary kiln for processing several types of raw material

Plant No.3 (calcination plant) for synthetic bauxite is already at full production, and in the same plant we produce our synthetic mullite (73% Al2O3), approximately 1,000 tpm. Investment in this plant was to change the production route from dry to wet.

And for the future?

Togni is in the process of doubling refractories production capacity with a total investment of >$20m. This plan started about two years ago, before the world crisis. The idea is to jump from 60,000 to 120,000 tpa of capacity to be ready to supply the Brazilian market as new steel projects come to fruition.

How is market demand?

The market not only for kyanite and mullite, but also for other regular refractories is recovering from the severe crisis, and if the new steel projects in Brazil keep their pace, we will have to increase production of kyanite.

Describe Togni’s position in the South American market?

Togni has a market share of 7-10% of the Brazilian refractory market, supplying shaped and unshaped refractories for virtually every market. We have some 5-10% exports in our sales, mainly to the South and Central Americas.

How do you view the main challenges facing refractory producers?

Raw material is the main challenge. As the customers are getting bigger every time and the raw material suppliers are selling their products with price controls based on search and demand, the one that can have their own raw material supply will have a closer cost control and therefore a better overall result.

One of Togni’s high alumina clay quarries
(60% and 55% Al2O3) in Popos de Caldas,
Minas Gerais, Brazil.

A view of Togni’s expansion (light coloured
building nearest with company sign) to Plant
No.1 at Popos de Caldas, which includes a new
milling system.