Cassiterite with Quartz

specimen number:
2072066

location:
San Antonio Mine, Viloco, La Paz, Bolivia

description:
Sharp lustrous translucent crystals of cassiterite measuring to 1.4 cm in size across the top of a crystallized quartz matrix. In good condition, minor damage present to some of the quartz crystals along the edge of the piece. Quite nice for this Bolivian classic.

The San Antonio Mine is located in the Viloco District of the Loayza Province, within the La Paz Department of Bolivia. Situated at extreme altitudes in the Quimsa Cruz mountain range, this site is a premier example of a high-temperature hydrothermal tin deposit. Geologically, the mineralization is hosted within Paleozoic metasedimentary rocks that were intruded by the granodiorite of the Viloco batholith during the Miocene epoch. The ore bodies consist of a series of narrow, steeply dipping quartz-cassiterite veins that formed as metal-rich fluids filled structural fractures. Historically, the mine was a significant producer of tin for the Bolivian economy throughout the 20th century, particularly under the management of the Patino mines and later the state-owned COMIBOL. The timeline of collecting reached a peak in the 1970s and 1980s, when miners began to systematically preserve the extraordinary cassiterite specimens encountered in the lower workings. These specimens are world-famous for their large, mirror-bright, jet-black crystals that often exhibit complex twinning, such as the classic elbow twin habit. While industrial production has fluctuated due to global tin prices, the San Antonio Mine remains the gold standard for aesthetic, lustrous cassiterite, with crystals often reaching several centimeters in size and possessing a brilliance that is unmatched by other tin localities.

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