Clausthalite with Eucairite

specimen number:
2262185

location:

description:

Masses of clausthalite and eucairite throughout matrix. Good rich example for the species. The specimen comes with a previous label from Ward's Natural Science Establishment. The specimen was originally acquired in 1973. Other species said to be present include tiemannite, umangite and uraninite.

The Predborice deposit, located near Trebsko in the Central Bohemia Region of the Czech Republic, is a classic European locality famous for its rare selenide mineralization, particularly clausthalite and eucairite. Geologically, the site is a hydrothermal vein deposit hosted within the contact zone of the Central Bohemian Pluton and Neoproterozoic sedimentary rocks, where low-temperature, uranium-bearing calcite veins became highly enriched in selenium. Within this unique geochemical environment, clausthalite (lead selenide) formed as metallic, lead-gray granular masses, while eucairite (silver copper selenide) occurred as microscopic inclusions and small, creamy-bronze aggregates, typically associated with crookesite and berzelianite. Historically, mining and underground quarrying operations at Predborice began in the early 1950s as part of a state-directed push to secure uranium resources during the Cold War era. Active extraction took place between 1951 and 1963, after which the mine was closed and the shafts were systematically sealed due to the depletion of viable ore.

Ward's Natural Science Establishment, founded in 1862 by Henry Augustus Ward in Rochester, New York, is one of the oldest and most influential scientific supply companies in the United States. Historically, it began as a pioneer in the field of taxidermy and the creation of custom geological and paleontological cabinets, rapidly becoming the primary supplier of mineral specimens, fossils, and cast reproductions to major museums and universities worldwide. The establishment played a critical role in the development of American natural history museums during the late 19th and early 20th centuries by outfitting institutions like the Smithsonian and the American Museum of Natural History. While its early history was defined by global expeditions led by Ward himself to gather rare mineralogical and biological materials, the company transitioned its focus mid-century toward educational supplies for secondary schools and academia. Through 2026, the company continues to operate as a major provider of science education materials, and its early historical catalogs and labeled specimens remain highly collectible artifacts that document the birth of academic mineralogy and systematic natural science training in North America.

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