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Potassium dichromate (synthetic).jpg
Category Sulfate minerals
(repeating unit)
Strunz classification 7.FD.05
Crystal system Triclinic
Crystal class Pinacoidal (1)
(same H-M symbol)
Space group P1
Color Orange-red, red
Cleavage Perfect
[010] perfect, [100] distinct, [001] distinct
Mohs scale hardness
Luster Vitreous
Streak Light yellow
Diaphaneity Transparent
Density 2.69 g/cm3

Lopezite is a rare red chromate mineral with chemical formula: K2Cr2O7. It crystallizes in the triclinic crystal system.[1][2]

It occurs as rare vug fillings in nitrate ores in association with tarapacáite (K2CrO4), dietzeite and ulexite in the Chilean Atacama and is reported from the Bushveld igneous complex of South Africa.[1][2] Lopezite was first described in 1937 for an occurrence in Iquique Province, Chile and named for Chilean mining engineer Emiliano López Saa (1871–1959).[1]

Most lopezite offered for sale to collectors is artificially produced.[1] Synthetic varieties also exhibit monoclinic crystals.[3]


  1. ^ a b c d http://www.mindat.org/min-2433.html Mindat
  2. ^ a b http://rruff.geo.arizona.edu/doclib/hom/lopezite.pdf Handbook of Mineralogy
  3. ^ 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