Dickite () is a phyllosilicate clay mineral named after the metallurgical chemist Allan Brugh Dick, who first described it. It is chemically composed of 20.90% aluminium, 21.76% silicon, 1.56% hydrogen and 55.78% oxygen. It has the same composition as kaolinite, nacrite, and halloysite, but with a different crystal structure (polymorph). Dickite sometimes contains impurities such as titanium, iron, magnesium, calcium, sodium and potassium. Dickite occurs with other clays and requires x-ray diffraction for its positive identification. Dickite is an important alteration indicator in hydrothermal systems as well as occurring in soils and shales. Dickite's type location is in Pant-y-Gaseg, Amlwch, Isle of Anglesey, Wales, United Kingdom, where it was first described in 1888. Dickite appears in locations with similar qualities and is found in China, Jamaica, France, Germany, United Kingdom, United States, Italy, Belgium and Canada. History In 1888, Allan Brugh Dick (1833–1926), a Scottish metallurgical chemist, was on the island of Anglesey to conduct research on kaolin. He performed various experiments describing the clay mineral. It was not until 1931 that Clarence S. Ross and Paul F. Kerr looked closer at the mineral and concluded that it was different from the known minerals of kaolinite and nacrite. They named it after the first person to describe the mineral. Composition is the chemical formula of dickite. The calculated percent abundances are very close when compared to other kaolin minerals. Chemical composition of dickite: 46.54% 39.50% 13.96% Dickite and other kaolin minerals are commonly developed by weathering of feldspars and muscovite. Through its evolution, dickite, a phyllosilicate mineral, maintains the aluminium and silicon elements influencing the formation of hexagonal sheets common to clay minerals. The problem of mistaken identity arises when comparing dickite to other kaolin minerals due to the fact that kaolinite, dickite, and nacrite all have the same formula but different molecular structures. The only way to determine the true identity of the mineral is through powder x-ray diffraction and optical means. Geologic occurrence Dickite was first discovered in Almwch, Island of Anglesey, Wales, UK. Dickite is scattered across Wales forming occurrences in vein assemblages and as a rock-forming mineral. This area and others where dickite can be found all share similar characteristics. Pockets in phylloid algal limestones, in interstices of biocalcarenites and sandstone are a suitable environment for dickite. Very low pressure and high temperatures are the ideal environment for the formation of dickite. The more perfected crystallization