MINERALOGY AND GENESIS OF THE COMBARBALIT A IN NORTHERN CHILE

Combarbalita is the local name of an ornamental stone formed by advanc ed argillic alteration of volcanic materials. Combarbalita is mined as a decorative stone from quarries that are near the town of Combarbala (31-degrees 19'S-70-degrees 59'W) in the Coquimbo Region. The rock is fragmented and shows flow-texture. The principal minerals are kaolini te and alunite, with minor presence of hematite and quartz. Its color is determined by the relative abundance of the following minerals or m ineral mixtures: hematite (reddish), hematite-kaolinite (pink-brown), kaolinite (white) and schlossmacherite (turquoise green). Combarbalita has unusually high concentrations of Sr, As and Pb (trace elements). The advanced argillic alteration that formed combarbalita, probably, o ccurred during the interval 80-70 Ma, which affected volcanic rocks er upted during Barremian-Albian time.