Lópezite is a rare, red, and carcinogenic chromate mineral with chemical formula: K2Cr2O7. It crystallizes in the triclinic crystal system.Lópezite data on MindatLópezite data in the Handbook of Mineralogy
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. Lópezite was first described in 1937 for an occurrence in Iquique Province, Chile and named after Chilean mining engineer Emiliano López Saa (1871–1959).
Most commercially available lópezite is artificially produced. Synthetic varieties also exhibit monoclinic 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
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