The mineral resources investing community in the Australian Stock Exchange (ASX) probably first heard of Halloysite when Andromeda Metals Limited (ASX: ADN) made news of their deposit in South Australia. I for one, certainly only heard of the term when I looked at Andromeda.
Did you know that up until 2005, the main use of halloysite was as an alternative raw material to kaolinite for ceramics? Today, there is an exponential increase in research aimed at halloysite Nanotubes (HNTs). The use of halloysite is almost synonymous to crying out:
"Oil that is, Black gold, Texas Tea" - [For those that remember]
As we move into 2022, there is only one other company, Suvo Strategic Minerals Limited (ASX: SUV), promoting the same story. It is a unique mineral and there is still a lot of misinformation and misunderstanding about the commodity and its potential uses. To add to the list of "issues" there is also a lot of mistrust of the potential use of the mineral.
Halloysite was named by Berthier in recognition of Belgium geologist J.J. d’Omalius d’Halloy who, in the early 19th century, collected samples of waxy, white clay at Angleur, Liége, which Berthier (1826) later analysed and described .
Halloysite is a 1:1 dioctahedral clay mineral that has been studied widely for applications in nanotechnology and as a mineral exploration guide for recognising regolith-hosted heavy rare earth element (HREE) deposits. 
Figure 1: (a) Straight, regular halloysite microtubles from Camel Lake. (b) Halloysite crystal morphology and atomic structure. (Photo 414524) 
According to , Halloysite is a relatively common mineral that often crystallises together with kaolinite; the two polymorphs of kaolin are not easily separated. Deposits suitable for commercial development are, however, comparatively rare and occur either as relatively pure masses of halloysite (e.g. Dragon Mine, Utah; Camel Lake) or as large, lower-grade sources from which halloysite can be readily separated (e.g. Matauri Bay deposits, New Zealand).
Figure 2: Geological setting of halloysite deposits formed by acid groundwater at the Camel Lake site, near Maralinga, South Australia.
As a geologist, I will say upfront, I know very little about halloysite and trying to explain the geological process is impossible for me. Doing research and trying to understand and then trying to summarise it is not an easy task. So there is going to be a lot of paraphrasing happening here.
Who is mining Halloysite?
As far as I know, there are very few people mining halloysite. According to my research, or what I have found, there are two "world-class" locations - Dragon Mine in Tinitc, Utah (USA) and the Matauri Bay deposit in Northland, New Zealand.
1) Matauri Bay halloysite deposit, Northland, New Zealand.
According to , halloysite clay deposits have been mined and processed in the Keriker-Matauri bay area of Northland since the late 1940s. Since the mid 1970s, this has been the dominant continuous supplier of halloysite worldwide, averaging around 20,000 tonnes per annum (tpa).
Figure 3: The very pure halloysite clay dug at Northland’s Matauri Bay is exceptionally white and bright. It is exported for use in high-quality materials such as porcelain, bone china and technical ceramics. 
The operation was acquired in 2000 by Imerys from former owners New Zealand China Clays Ltd. Imerys Tableware NZ Ltd currently mines raw clay from open pit mines developed in the Matauri Bay and nearby Mahimahi rhyolite domes (Fig. 4). The raw clay contains around 50% halloysite, 50% silica minerals (quartz, cristobalite, tridymite, amorphous silica), and minor feldspar.
Figure 4: Geological map of the Kerikeri – Matauri Bay region of North Island New Zealand (derived from Web Map (GNS Science, 2013) ) showing rhyolite domes and halloysite deposits, with sketch west-east section through the Matauri Bay halloysite deposit (after Brathwaite et al. (2012))
2) Dragon Mine 
Dragon mine is located in the Tintic District of north central Utah, some 60 miles southwest of Salt Lake City. The geology and details of alteration and mineralization at the Dragon mine are well described by several authors and the references can be found in . The host rocks are Upper Cambrian Ajax Dolomite and Opex Formation with underlying Middle Cole Canyon Dolomite and Tintic Quartzite (Fig. 5).
There are two main clay bodies at the Dragon mine – West and East as shown in Fig. 5. Dragon was originally an iron ore mine and subsequent mining of halloysite was mainly from underground during 1947– 1976 with 1.35 million tons mined by Filtrol.
Figure 5: Geological section, approximately west–east, through the Dragon mine, Tintic mining district, Utah, showing the distribution of halloysite ore zones – redrawn from Kildale & Thomas (1957) and Morris (1985).
Halloysite was extracted using a square-set method (5.2 × 6.0 × 7.8 ft) and hand-drills, and it was transported to the surface via a shaft and then loaded onto a lorry, which delivered raw clay to the Filtrol plant in Salt Lake City for processing into a fluid cracking catalyst
(FCC) for the petroleum industry.
Wilson and Keeling 2016  has Table 1 below which shows some of the halloysite sites around the world. Their work is pretty good in giving an idea of what is around. However, there have been several new players since Suvo Minerals identified halloysite on their Pittong Operations as well.
Table 1: Some halloysite and mixed halloysite-clay deposits.
There is a report in 2021 of a pegmatite in Brazil which has tubular halloysite and HREE (Heavy Rare Earth Elements), so discoveries are being made. As halloysite is chemically and physically different from normal kaolin-kaolinite, the identification of halloysite will happen more commonly. However, as you see how the categorisation/grading of these "clays" become clearer, the economic implication will cause many halloysite deposits uneconomical and hence, not important.
Grading Kaolin - Halloysite
The way industrial clays are considered to have technical and economic qualities is solved by the process of categorisation. In the market, we hear of the term "white brightness" to classify the quality of halloysites. In an article by Harvey and Keeling 2001 , there are four categories.
Category 1: clays of high quality requiring major capital investment to supply large tonnage, international markets. Produced in Georgia (USA), Conrnwall (UK) and the Amazon Basin in Brazil.
Category 2: unique specialty clays for which advanced technologies are required to produce small tonnages for niche markets. Clay deposits in this category are typically of high purity and are found in somewhat uncommon geological settings. Minerals such as Hectorite and Bentonite are common types within this category.
Category 3: moderate quality clays requiring relatively low technologies, to supply predominantly local markets.
Category 4: clays of low quality requiring little or no processing.
Harvey and Keeling 2001 concluded by noting that Categories 1 and 2 clay projects are of a higher quality which require extended development times (from green-field to investment decisions) and significant pre-development capital investment.
On the other hand, the development of Categories 3 and 4 clays requires shorter times and lower levels of capital investment.
According to the article, Category 2 is where halloysite sits. Interestingly, the article mentions the Maauri and the Poochera deposits as type areas.
Figure 6: Location of Australian and New Zealand clay deposits. 
There are no known hectorite in either Australia or New Zealand, although the geological setting of the North Island of New Zealand is in many ways similar to that of Nevada. Both Nevada and the central North Island of New Zealand have extensive areas of hydrothermally altered acid to basic volcanic rocks.
Interestingly, my previous understanding of Australian clay deposits (Figure 6) was that they were all uneconomic. According to this paper , I was not far off the mark. The majority of the Australian clay deposits sits in Category 3 and 4, which are the lower value. These deposits are largely deemed uneconomical due to their logistics and location to market.
The Significance of Halloysite
While doing research on this Insight, what is very clear to me is that there is a lot of momentum in this sector. Recently I did a Coffee with Samso with James Marsh, the managing Director of Andromeda Metals - Andromeda Metals Limited (ASX:ADN) - The Real Story. - where we talked about the misunderstanding of the strategy of the company.
In that Coffee with Samso, our discussion centred on the downstream part of the story which is the unique part of the whole halloysite story. It is, in fact, the emerging part of the Kaolin-Kaolinite-Halloysite sector.
Figure 7: The number of scientific papers written with each year up to 2015 according to the appearance of (a) halloysite (diamonds) or (b) halloysite nanotubes (HNTs) in the Article Title, Abstract or Keywords (both sourced from Scopus© database) and (c) numbers of patents filed per year with halloysite in Article Title or Abstract (source Espacenet) 
The chart in Figure 7 is a great way of showing the influx of research in the halloysite sector. I remember James Marsh telling me about the thousands of papers that have been written about this subject and the myriad of potential downstream products.
When I first had a conversation with Andromeda way back in 2019, I had no idea about the downstream process. I actually thought that it was more of a dream than a potential reality.
In the last Coffee with Samso with James, it was great that we put some layman's reality into the whole process. I feel this is an important for the halloysite message because there is a lot of confusion in the market. The confusion is born out of a lack of understanding of the downstream process and the myriad of potential products.
What Does All This Mean?
Players such as Andromeda and Suvo Strategic Minerals are in a space that is evolving. The emerging new "Industrial Revolution" that I spoke of in the latest Samso Insight - Expectations for the Mineral Resource Industry in 2022 - Green Energy and No Emission. - is going to drive more need for the humble Kaolin.
At the moment, in my opinion, the jury is still out in terms of the products from halloysite. I agree that there are many products which are at a pilot stage, like Andromeda, but the success or lack of is unknown. Science shows that through a step process of test and pilot plants, this normally ends well but there is no ´sure thing´ concept here.
One of the most updated places to get information on the downstream products would have to be the Andromeda Metals website. They have been the most active in promoting their vertical integration business model.
Table 2: Some present and future uses and applications for halloysite. .
The way Andromeda has separated their products is interesting. I think if we take the categorization observed in the paper by , I would fit them as follows:
Kaolin (Category 3 and 4),
Halloysite Kaolin (Category 2 and 3)
High Purity Alumina (Category 1 and 2)
Suvo Strategic Minerals is continuing to develop their Pittong operations and recently announced some upgrade in their Kaolin grades - Further High Grade Halloysite at Trawalla, Grades Up to 32.4% - which will be good for the company. However, I actually think that if you can get simple kaolin to the market, that is a great achievement by itself.
The Kaolin space is so active now that I think having an operation like Pittong is some of the advantage that Suvo has over their competitors. Like all mineral projects, an operation that is up and running is a lot better than just talking about it.
The information or opinions provided herein do not constitute investment advice, an offer or solicitation to subscribe for, purchase or sell the investment product(s) mentioned herein. It does not take into consideration, nor have any regard to your specific investment objectives, financial situation, risk profile, tax position and particular, or unique needs and constraints. Read full Disclaimer.
Samso is a renowned resource among the investment community for keen market analysis and insights into the companies and business trends that matter.
Victor Matheus Joaquim Salgado-Campos; Luiz Carlos Bertolino; Francisco José da Silva; Julio Cezar Mendes; Reiner Neumann, 2021, Mineralogy and chemistry of a new halloysite deposit from the Rio de Janeiro pegmatite province, south-eastern Brazil, Clay Minerals (2021) 56 (1): 1–15
John L Keeling and Pooria Pasbakhsh, Halloysite Mineral Nanotubes – geology, properties and applied research. MESA Journal 77 Issue 2 – 2015
Keeling JL 2015. The mineralogy, geology and occurrences of Halloysite. In P Pasbakhsh and GJ Churchman eds, Natural Mineral Nanotubes: Properties and Applications. Apple Academic Press Inc., New Jersey, pp. 96–112.
Brathwaite, R.L.; Christie, A.B.; Faure, K.; Townsend, M.G.; Terlesk, S. Origin of the Matauri Bay halloysite deposit, Northland, New Zealand. Mineralium Deposita 2012, 47, 897-910.
GNS Science. New Zealand Geology Web Map. http://data.gns.cri.nz/geology/ (accessed June 12, 2013)
Harvey, Colin C and Keeling, John, 2002 Categorization of industrial clays of Australia and New Zealand. Applied Clay Science 20, pp243-253.
Wilson, Ian and Keeling, John. 2016. Global occurrence, geology and characteristics of tubular halloysite deposits. Clay Minerals, Vol 51, pp 309-324.
Kildale M.B. & Thomas R.C. (1957) Geology of the halloysite deposit at the Dragon Mine. Pp. 94–96 in: Geology of the East Tintic Mountains and Ore Deposits of the Tintic Mining Districts (D.R. Cook, editor). Guidebook to the Geology of Utah, 12, Utah Geological Society, USA.
Churchman, G. Jock, Pasbakhsh Pooria, and Hillier, Stephen. 2016. The Rise and Rise of Halloysite. Clay Minerals, 51, pp303-308.