Worldwide halloysite deposits, production and market developments

By Ian Wilson

Halloysite is a 1:1 aluminosilicate clay mineral with formula Al₂Si₂O₅ (OH)₄. It was named in 1826 after Belgian geologist Jean Baptiste Julien d’Omalius d’Halloy, from an occurrence of the mineral discovered near Liége in Belgium.  

The main properties of halloysite are shown in Table 1.     

The hydrated form of halloysite is known as halloysite 10Å (a molecular size fraction measured in angstroms) and used to be known as 'endellite’, but this mineral name is no longer accepted.  Halloysite 7Å is dehydrated halloysite - a layer of interlayer spacing also referred to as 'metahalloysite’. 

Halloysite 10Å is the primary form with water in the interlayer space and this 3 Å thickness of interlayer water is lost rapidly and irreversibly in halloysite 7Å, as shown in Figure 1.    

Halloysite occurs in a number of different colours, as shown in Figure 2.  White halloysite is very pure and often hard and porcellaneous. The light brownish halloysite contains goethite, while the red halloysite contains hematite and the black and white halloysite contains blackish manganese.

Types of deposits

Hallloysite is encountered in a wide range of geological environments from the alteration of various rock types. Intrusive acidic rock types, such as granites, pegmatites and anorthosite, are coarse-grained as they cooled slowly with potash and sodic feldspars, subsequently being altered to kaolinite, halloysite and other clay minerals by a combination of hydrothermal and meteoric fluids.    

In New Zealand, extrusive acidic volcanic rhyolite is fine-grained as it cooled quickly and the feldspar altered to halloysite. In China, Turkey and the US, zones of up to 100% are present and found as a result of precipitation of alumina (Al) and silica (Si) solutions derived from volcanic and igneous  activity.    

Deposits will be considered on basis of those with high levels of halloysite and those with a mixture of kaolinite and halloysite

Deposits with high levels of halloysite 

The locations of high quality halloysite deposits currently mined are in China, Turkey, New Zealand and the US, as shown in Figure 3.

Applied Minerals Inc.’s Dragon Mine, US

Applied Minerals’ Dragon Mine is located in the Tintic district of north central Utah in the US, some 75 miles (121km) southwest of Salt Lake City. Geologically, the Tintic quartzite is about 513m years (Ma), Ajax-Opex dolomite from around 500-488 Ma, intrusion of Silver City monzonite is about 33.6 Ma; iron ore is probably the last gasp of the monzonite around 33 Ma.  The volcanics range in age from 33.9-18 Ma, but the andesites and latites nearest to Dragon are basically coeval with the monzonite, which intrudes them, so they are about 33.8 Ma¹. 

From 1947 to 1976, more than 1.35m tonnes halloysite was sold from the Dragon Mine into the fluid cracking catalysts (FCC) market. Mining was carried out by Filtrol Corp. on a contracted basis for the property’s owner, a subsidiary of Anaconda Mining Co. Activity came to a halt following an underground fire in 1976. 

More recently, exploration was carried out in 2003, 2005 and 2006 and with new management from 2008, drilling and characterisation of the core commenced in 2009 and is ongoing. 

Measured resources of clay are 2.2m s.tons with 0.63m s.tons high quality, 94% halloysite from the Dragon Mine and a further measured resource of 1.57m s.tons mixed kaolinite, halloysite and illite-smectite from the company’s Dragon and Western mines and from a stockpile of waste material. The detailed work carried out to date has given Applied Minerals confidence that the resources are sufficient to sustain an economic operation at the site and a mine permit has been granted covering an area of 266.7 acres (1.1km²). 

Scanning electron microscope (SEM) analysis of pure white halloysite from the Dragon Mine is shown in Figure 4. The morphology is mainly tubular, with tubes ranging from 50-1,000nm with some cylindrical tubes.     

The detailed characterisation of the clays from drilling in 2009 and 2010 led to the development of a new underground mine in Dragon Pit, with a portal commencing in August 2010. 

Iron ore is removed and used to produce iron pigments (trademarked and sold as Amiron), while the halloysite is mined by the square-set method, where a square block measuring 8x8x8 ft is removed and replaced by a 'set’, or cubic frame of timber, which is immediately put into place.      

Material is currently processed through dry milling to produce halloysite products trademarked as Dragonite suitable for use as a flame retardant in plastics, as well as a nucleating agent in plastics, coating and additives, cosmetics, catalysts, ceramics, water purification, extended relief carriers, proppants and other uses.

Many of the products are new to the market and have been commercialised following a great deal of research.  

The Dragon Mine has a fully equipped laboratory with Bruker X-ray fluorescence (XRF) and X-ray diffraction (XRD), Mircomertics sedigraph for particle size determination, Micromeritics Brunauer-Emmett-Teller (BET) surface area and porosity, Datacolor, a Hegman tester and other equipment. Since 2010, Applied Minerals has announced joint venture (JV) and cooperation initiatives with various companies, as follows:

• December 2010: Joint development agreement with Klibbe Chem Inc. for Masterbatch Manufacturing.

• March 2010:  US Naval Research Laboratory awards Applied Minerals a licence for patents covering the use of halloysite microtubes, with applications such as anti-fouling boat hulls which use biocides to reduce barnacle growth.

• February 2011:  Supply contract for Dragonite-HP product with Signature Fencing & Flooring Systems LLC to utilise as an additive in its MegaDeck product for heavy-duty matting and temporary roadway systems.

• June 2011: Enters into a collaborative research and development agreement with US Environmental Protection Agency aimed at finding a remediation solution for oil contaminated marshland.

• November 2012:  Signs letter of intent with HCT Group to form cosmetics JV to use Dragonite-PureWhite product in applications such as fragrances, deodorants, colour cosmetics, nail products and extenders.  Dragonite-PureWhite is effective without an active agent, owing to its high surface area, cation exchange capacity and porosity, which makes it particularly effective at absorbing excess oil and toxins from clogged skin pores. Independent laboratory studies have validated the effectiveness of halloysite as an effective acne bacterial reagent.

• April 2013: Signs agreement with Sigma-Aldrich Corp. to distribute Dragonite product to researchers worldwide.

• June 2013: Announces memorandum of understanding for a distribution/agency agreement with Mitsui Plastics Inc. to market, sell and distribute Dragonite.

Eczacibași Esan, Turkey 

Esan extracts halloysite from five different locations in northwest Turkey. There are two principal pits at Turplu and Taban, with three smaller occurrences at Ilicaoba, Kanasu-Kabalkar and Şahbas - all in the province of Balikesir.   

Production of high quality halloysite is estimated at 5,000 tpa and some material is shipped from Bandirma, on Turkey’s Marmara Sea coast. Extraction takes place in open pits with small scale galleries and shafts. Excavators are used for stripping overburden  while hand-picking selects the whitish halloysite.

All of Turkey’s halloysite deposits are associated with the Miocene volcanics of northwest Anatolia and formed at the contact between the Jurassic limestone and the andesitic volcanics.   

The larger deposits are stratiform between a limestone basement and the overlying volcanics. The volcanics are altered by hydrothermal activity with the formation of the halloysite, probably caused by precipitation directly from aluminium- and silica-rich acidic fluids. Pyritisation on the contacts to the halloysite bodies, recrystallisation of the limestones and dissemination of the manganese material at the contact with the limestones are part of the processes that give rise to the halloysite. Alunite, gibbsie and illite are accessory minerals associated with the halloysite. 

Details of some of the deposits are as follows:

Turplu 

The Turplu mine is located approximately 25km west of Balikesir with two main quarries. Minor amounts of gibbsite are the main accessory of halloysite in this deposit with some of volcanics altered to kaolinite.   

The output of Turplu is estimated at up to 2,000 tpa. Hard hand-picked whitish halloysite from the deposit’s No 2 mine is up to 100% halloysite in small samples, often with quartz, alunite and gibbsite as accessory minerals. A small proportion of the ore has low iron oxide (Fe₂O₃) content of around 0.15%, with titanium dioxide (TiO₂) at 0.01%. For slightly iron-stained halloysite, the Fe₂O₃ is 0.45%.    

The material’s surface area is around 70-75 gm/cm². An SEM of the Turplu halloysite, shown in Figure 4, indicates distinct tublar morphology of the hydrated halloysite. 

Esan’s other deposits are located at Ilicaoba, Kanasu-Kabalkar and Şahbas, with levels of production dependent upon sales. Hand-picked soft whitish halloysite from the Ilicaoba mine has some zones with low Fe₂O₃ at 0.17%, with TiO₂ at 0.01% and for iron-stained halloysite the Fe₂O₃ is 0.86%. Surface area ranges from 47-74 gm/cm².

Guizhou province, China 

In China, there are small deposits of halloysite in Guizhou province and some occurrences in Hunan and Yunnan provinces.

In Guizhou, there are four areas of halloysite in Dafang, Qingxi, Sunyi and Shijin. Dafang has many occurrences of halloysite as a result alteration of volcanic rocks adjacent to limestone. Alumina-silica solutions passed along fractures and faults and, on cooling, crystallised to halloysite.

The halloysite is often iron-stained and is mined by local workers. The deposits occur in pockets and mining is carried out in circular trenches about 1-2 metres wide and down to 5-10 metres in depth.   

Mine workers working individually or in small groups hand-pick on the basis of colour; probably only 10-20% is whitish with the rest being iron stained. The better material at around 25-30% moisture is put into sacks and taken to an area where it is partially dried and hand-picked again (Figure 6).    

Very little is wasted as all the iron-stained halloysite is sold for ceramics. The whiter halloysite is sold in lumps for use in porcelain. The lump halloysite is generally hard with whitish and some with bluish colours. Grade A material has 94-99% <2 µm, surface area from 60-70 gm/cm², 0.10 % Fe₂O₃ content and <0.01 TiO₂ content with a loss on ignition % (LOI) of 15-16%. Mineralogically, the material is around 99% halloysite with 1% quartz.  

Some of the Guizhou halloysites have a bluish tinge, which disappears on drying.  Production from the area is small, at around 2,000 tpa, and the halloysite is utilised, mainly by ceramic companies in China, to enhance fired brightness and increase the strength of porcelain due to its inherent fineness and large surface area.  

Some of the halloysite is also exported to Japan and Korea for use in bone china and porcelain.

Imerys, New Zealand 

The Kerikeri-Matauri Bay area of Northland, North Island, New Zealand, 250km north of Auckland, has been a source of halloysitic clays for ceramics over 60 years.

New Zealand China Clay Company (NZCC), which mines halloysite in the area, was acquired by France-based Imerys in 2001. The Northland halloysite deposits are all within alkaline rhyolite domes emplaced during the youngest phase of volcanism, which commenced in the late Miocene and continued into the late Pleistocene.    

In 1969, a wet process plant was installed at the Matauri Bay deposit and since the mid-1970s, this has been the main supplier of halloysite worldwide, with an output of up to 15,000 tpa. The plant is supplied from open pit mines at Matauri Bay and nearby Mahimahi rhyolite domes.  Due to the extrusive nature and high temperature of formation, the matrix of quartz and feldspar crystallised rapidly giving a fine-grained assemblage of halloysite (alteration of feldspar), quartz and cristobalite. 

The halloysite is blended from stockpiles and wet ground in pan mill to a size fraction of <5 mm. This is followed by autogenous grinding at high solids and then by hydrocyclones and settling boxes which are followed in turn by centrifuges to reduce levels of fine-grained silica.    

The clay is thickened, pressed and filtercake is either extruded at 37% moisture or shredded and dried to produce granules and powders. NZCC Premium is mainly destined for bone china and porcelain manufacturing, with key properties of brilliant brightness, high translucency, reduction of fired sag and low iron and titania, forming part of Imerys Ceramics’ product portfolio.  

A typical analysis of NZCC Premium halloysite shows low Fe₂O₃ (0.25%) and TiO₂ (0.07%), which gives rise to high fired brightness at 97 (1,180°C) and 98.7 (1,280°C), fine particle size of 95% <2 µm with 0.5% >10 µm.  

BET specific surface area is 27.8 m²/gm. Mineralogically, the halloysite ore is 88% halloysite, 2% kaolinite and 10% quartz/cristobalite. An SEM of NZCC halloysite in Figure 7 shows the presence of both tubular and cylindrical morphology with some platelets of kaolinite.   

Most of New Zealand’s halloysite is exported primarily for use in quality tableware, porcelain and bone china, with around 15% for technical ceramics for use in molecular sieves and in manufacture of honeycomb catalyst supports.   

In addition to the Matuari Bay and Mahimahi deposits, halloysite is present in other rhyolite domes in the district at Maungaparerua and Shepherd’s Hill. The largest dome is Maungaparerua, with alteration of the rhyolite a mixture of quartz, halloysite and alophane with minor plagioclase feldspar. 

The iron oxide titania content is higher than that of the halloysite at Matauri Bay and Mahimahi, probably due to the dome intruded into an overlying basalt (high in titania and iron), which became assimilated into the rhyolite. Consequently, the quality of this material would not be as suitable for use in bone china and porcelain. 

Mixed halloysite and kaolinite deposits 

A list of some companies, locations, types of deposit, mineralogy, main markets and estimated capacities for existing operations are shown in Table 3. This is not a comprehensive list of all deposits, but gives an idea of some of the markets served by halloysite, with the major market being ceramics, and shows how quality varies depending on the end-use.   

For example, Longyan Kaolin Company in Fujian, China, produces a whitish, coarse-grained mix of tubular halloysite and stacky kaolinite resulting from alteration of the feldspar in the granite. The clay is used primarily in tableware and porcelain due to the low levels of iron and titania in the altered granite. In Thailand Imerys-MRD produces a clay in Ranong with exceptionally high casting properties used in sanitaryware due to the alteration of a coarse-grained granite giving large halloysite tubes up to 20 µm in length. 

In Brazil, mixed halloysite-kaolinite is formed by alteration of pegmatites in many small deposits in Minas Gerais state. A weathered anorthosite near Encruzilhada in Rio Grande do Sol is also an example of a mixed deposit.

Mineração Horii Ltda, based at Jundiapeba, east of São Paulo, has been a major producer of kaolin in southern Brazil for paper filler clays, ceramics and fibreglass. For 20 years from 1981-2001, filler clay was supplied to major paper groups, but this business came to a halt with the switch to using PCC as the filler.  However, Horii still sells some clay for paper with the main output being for fibreglass, ceramics and other uses.     

Development of new markets for halloysite

The tradional uses of halloysite were mainly limited to ceramics and, in the past, catalysts. Reseach on halloysite as a naturally occurring nanotube has been published in over 600 papers, with almost 7,000 citations in the fields of chemistry, material science, polymers and engineering.

Many of the potential new markets require a pure halloysite such as that found in China, Turkey and the US.  The extent and richness of halloysite resources in China are not known and there is limited information on Turkey, although the deposits that have been explored are quite small and pockety and need to be hand-picked.  

The high grades necessary for new markets are only available in a small proportion of resources. Although the bulk of the material is still utilised, the price differential between this and high purity halloysite is substantial.  

A list of present and future uses and applications for Halloysite in in Table 3.

References:

^1. Personal communication Ken Krahulec, Utah Geological Survey. 

*Ian Wilson is a consultant based in the UK.