27 September 2007
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New horizons for Wonderstone

John Connelly
John Connelly
Ottosdal is a small town in the North West province that Mining Weekly passes through on the way to places such as Black Mountain or Beeshoek, or the mines of Namibia.

What is little known is that ten minutes’ drive to the north of this dusty hamlet is a remarkable mining and processing operation.

The market capitalisation of this company is some R100-million – not a large operation, when compared to the gold-mines further north.

However, the Wonderstone operation could be a model for its larger cousins in the minerals industry.

While Minerals and Energy Minister Phumzile Mlambo-Ngcuka calls on the mines to add value to their ores or metals, Wonderstone, with a healthy dash of home-grown ingenuity, has been turning a low-value mineral into high-value products for many years now.

Recently, the mine has undergone a transformation, moving from being a natural stone quarry to being a high-tech producer of finished goods.

The rock that is mined at Wonderstone is correctly termed pyrophyllite, a name derived from the Greek words for ‘fire’ and ‘leaves’, as the rock exfoliates readily when exposed to flames.

The slatey rock has a slightly slippery feel, and is, basically, aluminium silicate in the form of ametamorphosed clay originally derived fromvolcanic ash.

On surface, where weathering has taken place, the stone is light grey; however, as one goes deeper in the deposit, the grey colour becomes darker.

This is due to a higher carbon content, but this does not seem to alter the commercially-exploitable qualities of the material.

The ash was laid down in layers, something which led to its earliest use.

Early farmers in the area came across the outcrop on the farm Gestoptefontein and found it was a simple matter to lever off uniform slabs of the rock for use as gravestones.

As the stone was soft (1 on the Mohs scale), it was easy to carve the names of the deceased in the yielding material.

Interestingly, though the stone is soft, it does not weather easily, explains Desmond Sacco, chairpersonof Assore.

The deposit occurs in the form of a low hill some 4,6 km long. Geological action has tilted the deposit so that the laminations in the body dip at about 80˚.

In terms of life-of-mine, the deposit has been drilled to a depth of 192 m to give a reserve of some 80-million tons.

At present, the mine moves about 40 000 t a month.

The rock is heavily flawed and, in terms of use of the natural stone, about 2% of the deposit is usable.

Early miners used wire-rope saws, which they stretched over the crown of the hill, to saw out slabs, a painfully slow procedure. At one stage, a mobile circular stone saw was brought in to cut large one-metre cubes from the face.

Although the blocks looked flawless, all too often, when they reached the factory, an undetected hairline crack rendered the block valueless.

Today, the mine uses a mounted hydraulic hammer to lever slabs loose. This more vigorous separation method defines which chunks of rock are usable at source.

The mine is neatly maintained, with excavation being from 100-m-long 8-m-high benches. A Komatsu shovel loads the slabs of rock into either a Bell or a Caterpillar dump-truck, to be hauled to thefactory.

An eye for an opportunity

Guido Sacco (father of the current Assore chair-person, Desmond Sacco) the founder of the Assore group of companies, apparently saw the tombstone quarry and realised the value in this versatilemineral.

Though pyrophyllite is not a geological rarity, the Gestoptefontein deposit is of a particularly high purity and volcanic in origin, and is the only A grade deposit in South Africa.

In 1937, Wonderstone was incorporated as a company.

The rock has good thermal insulation qualities. It can also tolerate high degrees of thermal shock and has a low coefficient of thermal expansion. It is also very fine-grained and is a poor conductor of electricity.

In industrial-diamond manufacture, the ingredients for a diamond have to be placed in a crucible and subjected to high pressure and heat.

Wonderstone is ideal, as it is sufficiently inexpensive to allow for the once-off use of the crucibles.

What is important is that wonderstone has a consistent density and hardness so that the quality of the crucibles remains consistent.

Any fault in a crucible can result in tremendous energy releases, which can easily damage the costly anvils that apply the required pressure. Supply of crucibles to the synthetic-diamondindustry was the foundation of Wonderstone’s early financial growth.

About three years ago, Wonderstone started to make inroads into the ceramics industry.

It was realised that wonderstone was a good natural ceramic with some excellent inherent qualities.

One of the products that was looked at was using powdered pyrophyllite with a binder as an alternative to formed basalt, which is used as a low-cost wear-resistant medium.

The wear properties of wonderstone are equivalent, while its cost is considerably less.

Wonderstone had the opportunity to buy out a ceramics company, Ceramox, of the East Rand, which allowed the new owners to tap into a sound source of expertise.

At Wonderstone, in the meantime, ultrahigh-pressure presses were installed to begin the manufacture of alumina wear tiles.

The rapid growth in this market surprised even the people at Wonderstone, explains John Connelly, Wonderstone’s director and GM.

The French connection

The most recent development in the life of Wonderstone is the signing of an agreement with the French corporate, Saint-Gobain, a world leader in glass and wear-resistant technologies.

While the agreement was signed in Johannesburg, Wonderstone had been in discussion with the French for nine months previously.

The benefit that Saint-Gobain brings to Wonderstone is twofold. “From our side, this gives us access to their technical expertise, such as their computer-aided design facility and high-powered research and developmentfacility,” says Connelly.

The group has a multimillion-dollar investment in test and lab equipment.

Connelly and his team are now tapping into this department to try and find new applications and markets for wonderstone.

The results on the first batch of wonderstone that was sent to the US for testing have recently been returned to the Ottosdal company.

The tests included baseline characterisation to investigate broader uses of the material.

The wonderstone was subjected to rigorousacid-testing, which gave promising results. Finally, the Americans carried out a wear comparison with wear-resistant material made from basalt.

When it is used in pipes carrying abrasive slurries, the alumina material would be used on the bends and the basalt material on the straight sections.

However, initial indications are that a Wonderstone alumina could be cheaper to produce, whiledelivering a product that will match basalt in wear applications. “In terms of capital items, we have installed and commissioned a new 500-t uniaxial press which is predominantly used in the manufacture of alumina wear-resistant tiles,” explains Connelly.

This freed up the original 500-t press, which is also used to carry out more specialised orders. The factory has also bought and commissioned an extruder, which is being used for the production of acid-resistant tiles.

The long-term view is that the extruder will be used for manufacturing a product that will be in either tile or tubular form.

The prospects for a wear-resistant pipe-lining that will ultimately replace the basalt product look promising.

Wonderstone has also boughtanother furnace, which is installed and working.

All of the three Wonderstone kilns at the moment are ‘top hat’-type units, where the heating elements are housed in a box-like structure, which is raised and lowered over the packed furnace loads.

This limits the factory to batch-processing only. Indications are that, with increased production, a continuous-firing kiln will be needed.

With the new kiln, if another similar unit is placed in line, firing can then be carried out continuously.

The factory is also spending ‘severalmillion rands’ on the purchase of a spray dryer and two ball mills.

“The spray dryer will be used for alumina wear-resistant tile production, but we also see a large benefit in employing that equipment to manufacture spray-dried wonderstone powder,” says Connelly.

The largest short-term demand for reconstituted wonderstone is in the making of the crucibles that are, in turn, used in polycrystalline-diamond manufacture. At the moment, the 300 000 crucible components that are produced every month are 75% manufactured from the natural stone. However, Wonderstone is keen to introducecustomers to crucibles made from reconstituted wonderstone – pyrophyllite powder which has been combined with a binder, pressed and fired.

Wonderstone is working closely with its customers abroad to perfect the powder-formed crucibles.

“Where the ball-mills play an important role is when we take material from our fines stockpile and run this into the ball-mill, a very controlled dosage of binder can be achieved,” continues Connelly.

From Wonderstone’s experience of its 36-hour cycle in the ball mill, it is possible to control the moisture levels and binder levels closely.

The feed from the ball mills will be pumped into the spray dryer, which then gives a closely-defined particulate size, where each particle is uniformly coated withbinder.

The mix is consequently homoge-neous.

Previously, although the factory had an efficient high-energy mechanical mixer, the binder tended to concentrate in certain areas of the mix.

The product from the ball-mill is an easy-flowing material, so one gets a much better fill in the dyes and bags used in the isostatic press.

There is also a saving to be made on thealumina.

“At the moment, we buy-in ready-to-press alumina powder; however, in the future we will be able to buy a calcined powder,” says Connelly.

The calcined material will be milled and combined with wonderstone, with the final product being spray-dried.

The cost advantage here will be in the region of 25%.

A further capital item could be another large calciner, which will be dedicated to making the wonderstone powder, as this is seen as a growth opportunity.

With the investment that Wonderstone has made in the drying ovens, the factory is now able to limit the amount of warping that happens during kiln firing.

From train brakes to aerospace

Although Connelly believes that there will always be demand for the pyrophyllite in its natural state, the rock in itspowder form is where the future for the company lies.

The company has some two-million tons of wonderstone already mined and lying in stockpiles.

The Ottosdal operation has a powder plant, which consists of a feeder-breaker or hammer crusher, which feeds two jaw crushers which, in turn, feed two hammer mills.

The plant, though it is on Wonder-stone’s property, was originally owned by De Beers, which used the powder in industrial-diamond manufacture. Subsequently, Wonderstone bought the plant and has diversified its customer base.

An illustration of the versatility of wonderstone powder was seen in a corner of a factory, where a technician was making a range of acid-resistant lab ceramics using the ancient method of slip-casting.

The powder is mixed with an alumina slurry and then poured into slip-cast moulds and, once the mouldings are dry, they are fired to make a hard ceramic product.

“We have recently developed quite a healthy local market for calcined wonderstone powder, which is finally used in train brake pads, a side of the business that is set to expand significantly with good export potential” When the Saint-Gobain delegation carried out the site visit to Ottosdal, discussions were held on using the company as a conduit for exports of calcined wonderstone to North America.

The other potential – and here Wonderstone is only starting to scratch the surface – is in the use of wonderstone in mould coats in the foundry industry.

Saint-Gobain itself is a major user of mould coats with its involvement in the glass and high-tech materials industry.

Another application which caught the attention of the Saint-Gobain delegation was the Wonderstone chromic-acid purification pot.

The purification pot is required to regenerate chromic acid, which is used in the chrome-plating industry.

Chrome-plating plants have the problem that, with successive platings, the acid used in the process becomes impregnated with impurities such as copper and iron. The plating time increases, while the quality of the chrome-plating deteriorates.

The acid-purification pot is an electrolytic container in which the contamination of thechromic acid can be reversed.

This has the advantage, apart from the cost saving that is involved, of solving a serious environmentalproblem.

Saint-Gobain has already made contact with several potential customers for this Wonderstone innovation.

“While we have some local customers that are delighted with the performance of the pots, in the next six months we will be into North America with some trial samples,” says Connelly.

The original powder plant will continue with its current customer base, while the new powder plant, which will be sited next to the new factory, will be used to service the new product ranges.

The growth at Wonderstone has been in both the natural and the reconstituted product. “Both the machine shop, with its computer numeric control turning and milling centres, and the Ceramox side have shown phenomenal growth,” expounds Connelly.

“It is a good sign when you start growing out of your buildings,” he adds.

“None of us in the Wonderstone team believe that we have even scratched the surface when it comes to the applications for the material.” The application for Wonderstone is almost as broad as the imagination.

However, Wonderstone is staying away from consumer-type products, concentrating on high-tech applications.

There are many markets where Wonderstone can replace existing materials in longevity and costs.

“I am excited about the relationship with Saint-Gobain and the potential it has for both com-panies,” says Connelly.

The rapid growth of Wonderstone is illustrated by the fact that, in 2003, the company spent R10,5-million oncapital items.

Some R21-million is being spent in the next year on capital projects.

The capitalisation of Wonderstonehas grown exponentially over the last couple of years, explains Connelly, to a point where the company has a capitalisation near R100-million.

A characteristic of the operation is the levels of ingenuity that are apparent.

The isolation and the singular nature of the operation have compelled it to rely on its own resources.

“We cannot go out and see what our competitors are doing because, in South Africa, there is no one to compare against,” explains Connelly.

Today, Wonderstone can boast a workforce that is dedicated and a staff turnover that is also very low.

The operation has a labour force of 160, which has grown from about 90 people just more than a year ago.

Currently, the operation makes some 200 components; however, Connelly sees no reason why this should not expand by leaps and bounds in the future.