Opal

specimen number:
1052793

location:
Dubnik, Cervenica, Presov, Presov, Slovakia

description:
Attractive precious opal on matrix. Previously from the collection of Wilhelm Hoyer, this dates to the 19th century. The specimen comes with an antique label as shown at the end of the video. A neat historical specimen from central Europe.

The Dubnik mining area, situated near the village of Cervenica in eastern Slovakia, is a historic locality famous for producing exceptional precious opal specimens. Geologically, the deposit is hosted within late Miocene volcanic rocks, specifically altered andesite flows and tuffs belonging to the Slanske Vrchy mountains. Hydrothermal solutions rich in silica circulated through fractures and cavities within these volcanic rocks, depositing thin layers of precious and common opal as vein-fillings and nested pockets. Historic records indicate that opal extraction occurred in the area for centuries, but systematic, large-scale industrial underground mining peaked during the nineteenth century under the lease of the Goldschmidt family, particularly from 1845 until 1880. Increasing competition from newly discovered Australian fields and economic pressures led to a steep decline in operations, culminating in the formal closure of the state-owned mines in 1922, though artisanal collecting and modern tourist diving in the flooded tunnels continue on a limited scale today.

Wilhelm Hoyer was a prominent nineteenth-century German engineer, architect, and professor based in Hannover who maintained a deeply dedicated parallel career as a mineral collector and amateur geologist. Born in 1836, Hoyer focused his private curatorial efforts on accumulating highly systematic mineral suites, with a specific emphasis on the regional mineralogy of the Harz Mountains, Westphalia, and the former Province of Hanover. His academic position at the Technical University of Hannover allowed him to collaborate closely with major mineralogists of the era, and his precisely organized collection served as an important scientific reference for documenting highly localized European occurrences. Following his passing in 1908, a significant portion of his meticulously labeled specimen catalog was integrated into institutional collections, including the University of Hannover, ensuring that his regional geological records remained preserved for future mineralogical study.

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