Clay minerals can be grouped into several classifications based on their characteristics. One of the groups of clay minerals is kaolin, which has one tetrahedral sheet and one octahedral sheet or can also be identified as a 1:1 clay mineral. Kaolinite, dickite, halloysite, and nacrite are the types of clay minerals that are included in the kaolin group minerals. They all have the same chemical formula of Al2Si2O5(OH)4.
1. Kaolinite
As one of the most ordinary kinds of clay minerals, the mining sites of kaolinite can be found in a lot of countries around the world. In fact, they are spread in every continent but the south pole’s continent, Antarctica.
In the United States, kaolinite can be mined in Brazil and the United States. Across the Atlantic ocean, the mines can be found in South Africa and Tanzania. In Europe, the United Kingdom, France, Germany, Bulgaria, Spain, and the Czech Republic have the mines as well.
Moreover, Asia also has a lot of countries among the kaolinite miners. Those countries are China, India, Pakistan, Malaysia, Indonesia, Vietnam, Bangladesh, Iran, and South Korea. Then, the smallest continent, Australia, also has kaolinite mines in it.
Related: The White Clay Mineral Kaolinite – Everything You Need to Know
2. Dickite
Dickite was discovered for the first time in 1888 on the island of Anglesey, Wales. It happened when a Scottish metallurgical chemist, Allan Brugh Dick, was doing research there on kaolin. The name was taken from the chemist’s name about five years after the chemist passed away in 1931 after the clay mineral was concluded to be a different kind.
Having the same chemical formula, dickite also has a similar percentage of chemical composition to other kaolin group minerals. It consists of 46.54% of SiO2, 39.50% of Al2O3, and 13.96% of H2O.
Dickite can be found across several areas in Wales, which have high temperatures and very low pressure, similar to the characteristic of its native land, Anglesey. This clay mineral can also be found in South America like Jamaica, San Juanito in Mexico, and Utah and Kansas in the United States.
3. Halloysite
Halloysite is usually found in locations with carbonate rocks nearby. Halloysite can be found particularly in volcanic ash and glass. The clay mineral is formed by the alteration of hydrothermal with moving waters. It usually happens in tropical and sub-tropical climates, like in Colorado, the United States.
Besides those characteristics and where to find it, it’s been said that the precise structure hasn’t been shown. Another interesting deal about halloysite is that while kaolinite, dickite, and nacrite come in plate form, halloysite materializes in a tubular form, with the possibility to have a single layer of its sheets according to research in USGS .
Halloysite has a great potential for future green technologies usage and for biomedical application in medical fields as well, just like kaolin clay.
4. Nacrite
Nacrite is a native German clay mineral. Specifically, it occurred for the first time in 1807 in Saxony, Germany. The name of the clay mineral is derived from nacre produced by nacrite’s surface when it receives direct sunlight.
In terms of forms, the nacrite has a polymorph or several different forms. With its dense variety, in China, nacrite is traded as a gemstone and used for carvings. Although it was a German native clay mineral, nacrite is also found in Canada and even Italy with the different forms mentioned earlier.
5. Allophane
There is one more clay mineral that comprises the kaolin, which is chemically similar to kaolinite but in terms of forms. This one is found as amorphous or not having a solid crystal form, or simply shapeless. According to Britannica, the mineral is called allophane. Allophane has chemical orders that contain silica, alumina, and water.
Originally located in Germany, similar to nacrite, allophane is also found in France, Greece, and Iceland. Based on scientific research, when allophane comes hand-in-hand with imogolite, it can be used to enhance soil storage. Future research for using allophane with its partner, imogolite, may support a technology development to take care of climate change issues.
While all of the facts mentioned above may seem complicated to understand but as kaolin group minerals, each of them hid a beneficial purpose, just like kaolin clay. Not only for common industries like construction but beyond, support for renewable or green technology that the world needs more and more.
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