Ryzí stříbro z Borovce (štěpánovský rudní revír)Článek v PDF
Native silver from Borovec (Štěpánov ore district)
Silver mining activities at Štěpánov ore district date back to 13th century. Besides the major ore minerals, the silver-bearing galenite with inclusions of freibergite, and the silver-bearing chalcopyrite, rare presence of native silver was encountered on dumps close to the shallow shaft Josef near Borovec (1 km N from Štěpánov). The mineralization occurs in quartz-carbonate veins cross-cutting marbles and metapelites. The native silver locally intergrows with native copper in quartz-calcite gangue or in quartz cavities; rarely, it is enclosed in cuprite or chrysocolla. Malachite and iron oxides and hydroxides are common constituents of the assemblage but in a small volume. Chemically, the native silver is very pure (~99 wt. % Ag) and except of low amounts of Cu (≤ 1 wt. %) it contains only traces of As (≤ 0.5 wt. %) Bi (≤ 0.13 wt. %).