How do I identify Dickite?

Dickite can be identified by its hardness of 2 - 2.5 on the Mohs scale, White color. Look for these key characteristics when examining specimens.

What color is Dickite?

Dickite typically appears in White, or tinted by impurities. Color can vary depending on impurities and formation conditions.

Dickite has a hardness of 2 - 2.5 on the Mohs scale. This makes it a soft mineral that can be scratched easily.

Dickite

A variety of Minerals

What is Dickite?

Dickite (Al2Si2O5(OH)4) 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.

Dickite Market Value Calculator

Estimate the market value of Dickite using size, quality, and finish. This preview calculator is for quick context and is not a formal appraisal.

Dickite Localities Map

See where Dickite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.

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North ZoneCentral RidgeSouth Basin

Key Characteristics

Characteristics of Dickite

Dickite takes on the appearance of a white, brown earthy color and is often found embedded in many other minerals such as quartz. Dickite has perfect cleavage in the (001) direction. Its color varies from blue, gray, white to colorless. It usually has a dull clay-like texture. Its hardness on the Mohs scale is 1.5-2, basically between talc and gypsum. This is attributed to its loose chemical bonds. It is held with hydrogen bonds, which are otherwise weak. It leaves a white streak and it has a pearly luster. It has a density of 2.6. Dickite is biaxial, its birefringence is between 0.0050-0.0090, its surface relief is low and it has no dispersion. The plane of the optical axis is normal to the plane of symmetry and inclined 160, rear to the normal to (0,0,1). The atomic structure of dickite, being very similar to that of kaolinite and other kaolin type minerals, has a very specific arrangement that differs slightly enough to set its physical appearance and other physical properties apart from that of its family members kaolinite and nacrite. In a comparison of the family of minerals through experiments examined by Ross and Kerr the similarities between them are clearly evident and can, depending on the samples, be indistinguishable by optical means. The hexagonal structure and the stacking of the atoms influence the physical properties in many ways including the color, hardness, cleavage, density, and luster. Another important factor in influencing physical properties of minerals is the presence of bonding between atoms. Within dickite there exists dominant O-H bonding, a type of strong ionic bonding.

Composition of Dickite

Al2Si2O5(OH)4 is the chemical formula of dickite. The calculated percent abundances are very close when compared to other kaolin minerals. Chemical composition of dickite: SiO2 46.54% Al2O3 39.50% H2O 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.