Mineralogy

Halite

Structural info:

halite2

Name origin:

The name is derived from Greek “hals” meaning salt.

Description:

Halite, also known as a rock salt is a water soluble mineral with a formula NaCl. Halite was the first mineral ever to be structurally studied by W. H. Bragg [1] back in 1912. It crystallizes in isometric system and forms well shaped cubic crystals. Octahedrally shaped crystals are less common. Rarely it is found in a form of stalactites and stalagmites [2]. The structure of halite can be described as a close packing of Cl. All the octahedral sites are occupied by Na+. Each Cl ion is surrounded by six Na+ and vice versa. 6:6 coordination is thus observed in structure [3]. It occurs typically in sedimentary rocks of evaporic association along with other water-soluble sulfates, halides and borates. Halite is usually colorless but blue halite has been found in the North America and in the Zechstein, Germany. This coloration is caused by gama-bombardement by associated potassium-40 found in sylvite or as written – followed by structure deformation [4].

halite1

Halite – unit cell [5]

nacl

Halite crystals, Wieliczka mine, Wieliczka, Malopolskie, Poland [photo: Michal Hegedus]

Literature:

[1] Bragg, W. H., & Bragg, W. L. (1915). X rays and crystal structure. London: G. Bell.
[2] Spiroff, K. (1937). AN UNUSUAL OCCURRENCE OF HALITE. Mineralogical Society of America, 22, 931-933. Retrieved May 24, 2016, from http://www.minsocam.org/MSA/collectors_corner/arc/mihalite.htm
[3] Kutty, T. R., & Tareen, J. A. (2001). Fundamentals of crystal chemistry. Universities press.
[4] Zelek, S. M., Stadnicka, K. M., Tobola, T., & Natkaniec-Nowak, L. (2014). Lattice deformation of blue halite from Zechstein evaporite basin: Kłodawa Salt Mine, Central Poland. Mineralogy and Petrology, 108(5), 619-631. doi:10.1007/s00710-014-0323-9
[5] Walker, D., Verma, P. K., Cranswick, L. M., & Jones, R. L. (2004). Halite-sylvite thermoelasticity. American Mineralogist, 89, 204-210. Retrieved May 24, 2016.