High-end tableware and technical ceramic applications such as molecular sieves remain the key ceramics market for two halloysite quarries in Northland, but higher-tech applications could soon emerge. HUGH DE LACY scans the horizon.
Global tableware and technical ceramics manufacturers have over the past 30 years taken the place of the domestic paper-making industry as the main outlet for the halloysite raw materials produced at Imerys Ceramics NZ’s two Northland quarries.
Where once the Matauri Bay quarry, which has been in continuous production since the 1950s, supplied almost all its aluminosilicate clay to domestic paper mills as a filler, now most of it goes to manufacturers of high-quality tableware and technical ceramics in more than 20 countries.
The Paris-based multinational is eyeing up opportunities for markets outside of ceramics for its halloysite products, but New Zealand manager Mathew Arthur notes: “These developments are in the early phases of investigation.”
For now though, the ceramic clays Imerys is extracting and processing at its two active quarry sites west of the Bay of Islands are destined for the global ceramics market.
Halloysite clays are formed by generally low-temperature geothermal activity and subsequent weathering of volcanic rhyolite domes.
There are four known halloysite clay deposits in Northland, and Imerys operates quarries at two of them, Matauri Bay and Mahimahi, and also has extraction rights yet to be exercised at a third, Maungaparerua.
The Imerys sites contain halloysite and silica minerals in roughly equally proportions, though with depths the clay content decreases and there’s a corresponding rise in feldspar and silica.
The existence of these deposits has long been known, and in the 1950s a group of locals got Matauri Bay into production using a not-very-popular diesel-powered drying plant in the nearby town of Kaeo.
Nobody in Kaeo wept when an upgrading of the power supply allowed processing to be electrified and shifted to the quarry site, and a larger rotary drier installed which remains in operation today.
Air classifiers were also added to reduce the amount of silica in the product, which initially was used almost exclusively in paper production, both the broadsheet on which dailies are printed, and the glossy papers used by magazines.
The locals eventually sold the Matauri Bay quarry to Ceramco Corporation, a temporary high-flier born of Auckland’s Crown Lynn pottery, founded in 1929, and killed off by Asian tableware imports in 1989, in the wake of the lifting of Crown Lynn’s import tariff protection.
By then though Ceramco had carried out an exploratory drilling programme at Mangaparerua in a joint venture with Georgia Kaolin Mining, a clay miner in the southern American state.
The joint venture acquired Matauri Bay and in 1969 set up a pilot plant to reduce the silica content of the halloysite by wet processing.
It later added a calcination plant, and also acquired the Mahimahi site in the late 1980s on which a second quarry was established.
During the 1970s the focus of production shifted away from paper filler and onto the rapidly emerging Japanese tableware manufacturing industry which needed halloysite for its high-quality translucent porcelain.
Taiwan and Korea followed Japan’s lead, and from the late 1970s onward Ceramco largely quit the local paper industry to concentrate on this rapidly growing new market.
By 1981 capacity at the Matauri Bay pilot plant had to be increased, and again in 1987, in which year the company established a research and development laboratory to further diversify its markets.
This led to the addition of catalyst support honeycombs and molecular sieves to the product range, employing the clays’ other key attributes.
The Imerys Group bought Ceramco’s New Zealand China Clay Company in 2000, at a time when the diversified Ceramco’s businesses were being liquidated, and the company itself hocked off to Malaysian interests.
Since then Imerys has exported its Northland halloysites, with the Matauri Bay and Mahimahi quarries remaining in production.
Arthur told Q&M that Imerys Ceramics NZ sells the majority of its output direct to overseas manufacturers, with the remainder being supplied to the parent’s global network for onward distribution to manufacturers.
“The majority of what we sell has tableware as the main end-application, but supported by the technical ceramics market, predominantly molecular sieve manufacture.
“Our products are known globally for their consistently high quality,” Arthur said.
The ceramics markets supplied by the company are globally diverse and competitive, but the company has seen a slight improvement in sales in the past year.
Arthur said the company is highly conscious of the need to further diversify its product line, at both the local and global levels, “so innovation with related R&D is integral to the business”.
The multinational group is well placed to hook into new applications with its main research and development centres strategically located globally, and supported by regional laboratories and technical support teams.
The group has annual sales of €3.7 billion, operating income of €495 million, and nearly 15,000 employees at 234 industrial sites in 50 countries.
At Matauri Bay and Mahimahi the main quality parameters of the clay are its iron, which results in high fired whiteness and translucency, and low K20 which results in low deformation characteristics.The quarried material is crushed to less than 5mm, followed by high-solids wet grinding before coarse classification in hydroclones and settling boxes.
Spiral classifiers separate out the coarse silicas, which find uses in the local construction market.
The remaining clay slurry is then classified by centrifuges, with the high-silica underflow fractions contained in settling dams from which the supernatant containing the fine clay is recycled to the plant as process dilution water.
Finally the overflow from the centrifuges is de-watered, using a high-rate continuous thickener, then filter-pressed into cakes which are either extruded into 25 kilogram blocks at 37 percent moisture, or shredded and dried in the rotary drier to produce granules or powder.
The granules at five percent moisture are packed into 100 kilogram or 1050 kilogram containers, and the powder at three percent moisture into similar containers or 30 kilogram multiwall bags, before being shipped from Auckland and Tauranga in 20-foot shipping containers weighing up to 21 tonnes each.