Wikipedia
Lópezite
Lopezite is a rare red chromate mineral with chemical formula: K Cr O. It crystallizes in the triclinic crystal system.
It occurs as rare vug fillings in nitrate ores in association with tarapacáite (KCrO), dietzeite and ulexite in the Chilean Atacama and is reported from the Bushveld igneous complex of South Africa. Lopezite was first described in 1937 for an occurrence in Iquique Province, Chile and named for Chilean mining engineer Emiliano López Saa (1871–1959).
Most lopezite offered for sale to collectors is artificially produced. Synthetic varieties also exhibit monoclinic crystals.