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Lópezite is a rare red chromate mineral with
chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...
: K2 Cr2 O7. It crystallizes in the
triclinic crystal system class=skin-invert-image, 180px, Triclinic (a ≠ b ≠ c ≠ a and α, β, γ, 90° pairwise different) In crystallography, the triclinic (or anorthic) crystal system is one of the seven crystal systems. A crystal system is described by three b ...
.Lópezite data on Mindat
/ref>Lópezite data in the Handbook of Mineralogy
/ref> It occurs as rare
vug A vug, vugh, or vugg () is a small- to medium-sized cavity inside rock. It may be formed through a variety of processes. Most commonly, cracks and fissures opened by tectonic activity ( folding and faulting) are partially filled by quartz, calc ...
fillings in nitrate ores in association with tarapacáite (K2CrO4), dietzeite and
ulexite Ulexite (), sometimes called TV rock or TV stone due to its unusual optical properties, is a hydrous borate hydroxide of sodium and calcium with the chemical formula . The mineral occurs as silky white rounded crystalline masses or in parall ...
in the Chilean
Atacama The Atacama Desert () is a desert plateau located on the Pacific coast of South America, in the north of Chile. Stretching over a strip of land west of the Andes Mountains, it covers an area of , which increases to if the barren lower slopes ...
and is reported from the
Bushveld igneous complex The Bushveld Igneous Complex (BIC) is the largest Layered intrusion, layered igneous intrusion within the Earth's Crust (geology), crust. It has been tilted and Erosion, eroded forming the outcrops around what appears to be the edge of a great Ba ...
of
South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...
. Lópezite was first described in 1937 for an occurrence in Iquique Province,
Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
and named after Chilean mining engineer Emiliano López Saa (1871–1959). Most commercially available lópezite is artificially produced. Synthetic varieties also exhibit
monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...
crystals.Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason, and Abraham Rosenzweig: " Dana's new mineralogy", p. 692. John Wiley & Sons, 1997


References

Potassium minerals Chromate minerals Triclinic minerals Minerals in space group 2 Minerals described in 1937 {{oxide-mineral-stub