Quartz (19th century)

specimen number:
1052830

location:
Weiselberg, Oberkirchen, Freisen, Sankt Wendel, Saarland, Germany

description:
A beautiful 19th century cut and polished agate specimen for this locality. Formerly in the collection of Wilhelm Hoyer, this comes with an antique label as shown at the end of the video.

The Weiselberg, a prominent volcanic dome rising near the village of Oberkirchen within the municipality of Freisen and the district of Sankt Wendel, Saarland, Germany, is a classic historical mineral locality famous for its distinct igneous rocks and silicate varieties. Geologically, the mountain is a Permian-aged volcanic plug composed of a unique, fine-grained dacitic rock known as weiselbergite, which features a high glass content and embedded crystals of plagioclase feldspar formed by rapid cooling near the surface. Hydrothermal activity within the cooling lava generated gas-formed vesicular cavities that later filled with secondary silica, creating occurrences of agate, chalcedony, jasper, and amethyst. Localized mining and quarrying activities for these lapidary materials date back to Roman times, with a significant underground extraction period developing from the fifteenth century onward as miners drove specialized adits into the green-tinted rock to recover agates for regional cutting centers. Commercial gemstone mining eventually ceased as easily accessible deposits were exhausted and synthetic or imported materials emerged, leading to the establishment of the formal Weiselberg nature reserve in 1950.

Wilhelm Hoyer was an influential nineteenth-century German mineral collector, field geologist, and civil engineer who specialized in documenting the regional mineralogy of the Saar-Nahe region and adjacent territories. Throughout the mid-to-late 1800s, he built a systematic research collection by acquiring exceptional specimens directly from active railway cuttings, infrastructure projects, and local mining adits, with a strong focus on the diverse agates, jaspers, and iron minerals native to the southwest German volcanic fields. Following his death in 1893, his extensive, well-documented mineralogical holdings transitioned into major European institutional collections and regional university repositories, serving as an important permanent scientific record of historic European mining localities.

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