Amicite is a silicate mineral of the

zeolite Zeolites are microporous, crystalline aluminosilicate materials commonly used as commercial adsorbents and catalysts. They mainly consist of silicon, aluminium, oxygen, and have the general formula ･y where is either a metal ion or H+. These p ...

family. It has a general formula of K₂Na₂Al₄Si₄O₁₆·5(H₂O). Amicite was described in 1979 from specimens obtained at the Höwenegg quarry in

Immendingen Immendingen is a municipality in the district of Tuttlingen in Baden-Württemberg in Germany located on the Upper Danube. It is famous for the Danube Sinkhole. Geography Immendingen is located on the Upper Danube. On the municipal area are part ...

, Hegau, in the German state of

Baden-Württemberg Baden-Württemberg (; ), commonly shortened to BW or BaWü, is a German state () in Southwest Germany, east of the Rhine, which forms the southern part of Germany's western border with France. With more than 11.07 million inhabitants across a ...

, which is consequently its type locality. The name is in honor of

Giovanni Battista Amici Giovanni Battista Amici (; 25 March 1786 – 10 April 1863) was an Italian astronomer, microscopist, and botanist. Amici was born in Modena, in present-day Italy. After studying at Bologna, he became professor of mathematics at Modena, and in 18 ...

(1786–1863) a botanist,

physicist A physicist is a scientist who specializes in the field of physics, which encompasses the interactions of matter and energy at all length and time scales in the physical universe. Physicists generally are interested in the root or ultimate cau ...

, optician, and inventor of microscope optical elements.

Structure and optical properties

Amicite is

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

, so the crystallography has three axes of unequal length and the angles between two of the axes are 90 degrees and one is less than 90. Amicite is also pseudotetragonal with a=10.23, b=10.43, c=9.88, and d= 89, and belongs to the space group I2.It appears as small colorless crystals, formed by the rhombic prisms and , combined in such a way that the crystal appears to be a dipyramid. Amicite is classified as biaxial anisotropic so the velocity of light varies depending on direction through the mineral, as well as showing double refraction. The index of refraction is the geometric ratio of the angle of light entering the crystal (angle of incidence) over the angle the light is bent when it enters the crystal (angle of refraction). The index of refraction can be defined mathematically as n=velocity of light in a vacuum/velocity of light in the mineral. Amicite has three indices of refraction na=1.485, nb=1.490, nc=1.494. A minerals birefringence is defined as the difference between the highest and lowest index of refraction, amicite's birefringence is 0.009. Amicite is a zeolite mineral, the commercial uses of zeolites are a function its three distinct properties: absorption, ion exchange, and catalysis. Zeolites are also known for their ability to absorb and lose water without any effect on its crystal structure.

Occurrence

Amicite is a very rare mineral, known only in four locations in the world, the type locality, the Vostochnyi and Kirovskii mines in the Chibiny massif, Murmansk region (Russia), where the largest known crystals come from, and also the quarry from Las Urracas, on the El Arzollar volcano, Campo de Calatrava (Ciudad Real). In addition to being poorly distributed, it is very scarce in the four locations mentioned.

References

{{Reflist *Alberti, A., and Vezallini, G. (1979) The Crystal Structure of Amicite, a Zeolite. Acta Crystallographica, B35, 2866-2869. Zeolites Monoclinic minerals Minerals in space group 5