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Category Zeolite
(repeating unit)
Strunz classification 9.GC.05
Crystal system Monoclinic
Crystal class Sphenoidal (2)
(same H-M symbol)
Space group I2
Unit cell a = 10.26, b = 10.43
c = 9.90 [Å]; β = 88.32°; Z = 2
Formula mass 690.51 g/mol
Color Colorless
Twinning none
Cleavage none
Fracture Conchoidal
Luster Vitreous
Streak White
Diaphaneity Transparent
Specific gravity 2.18
Optical properties Biaxial
Refractive index na=1.485, nb=1.490, nc=1.495
Birefringence 0.01
References [1][2]

Amicite has a general formula of K2Na2Al4Si4O16·5(H2O).[3] The name is in honor or Giovan Battista Amici (1786–1863) a physicist, optician, and inventor of microscope optical elements.

Structure and optical properties[edit]

Amicite is monoclinic, 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.

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.


  1. ^ Barthelmy, David. "Amicite Mineral Data." Mineralogy Database. 1997-2010, 2 Nov. 2010. Web. 5 Nov. 2010. <>
  2. ^ Ralph, Jolyon, and Ida Chau. "Amicite." 1993-2010, 5 Nov. 2010. Web. 5 Nov. 2010. <>.
  3. ^ Handbook of Mineralogy. Mineralogical Society of America. 2004,
  • Alberti, A., and Vezallini, G. (1979) The Crystal Structure of Amicite, a Zeolite. Acta Crystallographica, B35, 2866-2869.