Tin-silver veins of Oruro, Bolivia, Part I

Abstract

The tin-silver ores of Oruro, Bolivia, are classed as xenothermal deposits. They occur at relatively shallow depths in complex veins in and adjacent to small stocks of quartz latite porphyry. Fracturing was closely associated with the process of mineralization. Erosion and deep oxidation developed a gradational capping of oxidized or 'paco' ores, composed of cassiterite, limonite, jarosite, and quartz at the outcrops of the primary sulphide veins. Tin is still mined from the oxidized zone, but the bonanza silver ores were mined out many years ago.