Sphalerite with Metallic Associated Crystals on Carbonate Matrix – Wiemannsbucht, Bad Grund, Harz, Germany
Size: 8 × 6.5 × 5.4 cm
Locality: Wiemannsbucht, Grund Mine, Bad Grund, Harz, Lower Saxony, Germany
Dark lustre, warm honey tones and unexpected windows of reddish-brown translucency give this richly crystallised specimen its distinctive appeal. Numerous sphalerite crystals are distributed across a sparkling bed of fine beige to honey-coloured crystals. In reflected light, they appear predominantly deep brown to almost black; favourable illumination reveals their warm reddish-brown body colour along thinner edges and translucent sections.
The varied crystal architecture rewards close inspection. Individual compact crystals alternate with closely intergrown groups, while smooth, brightly reflective faces contrast with finely stepped and textured surfaces. Metallic lead-grey associated galena provide striking accents throughout the display face. Pale, finely crystalline areas introduce additional contrast and bring definition to the darker ore minerals.
The specimen belongs to the hydrothermal lead-zinc-silver mineralisation of the Bad Grund district. Mineral-bearing fluids circulated through tectonic fractures in Lower Carboniferous greywackes and shales, depositing successive generations of ore and gangue minerals. Sphalerite and galena were the principal economic ore minerals, accompanied by characteristic gangue minerals including quartz, calcite and siderite.
The Wiemannsbucht provenance places this specimen within the historic Grund mining complex. Its closure in 1992 marked the end of the last operating ore mine in the Upper Harz.
An engaging specimen for collectors of classic German localities, combining richly varied crystallisation with subtle colour and historical significance. Its appeal grows with closer inspection, as changing angles reveal fresh reflections and reddish-brown translucency within the dark sphalerite crystals.
