Hidden within Freiburg’s embrace lies the Oberer Steinbruch. It’s a place where nature and history have woven an intriguing tale. This former quarry, whose name means “Upper Quarry,” whispers secrets of a time long past. It reveals a glimpse into Freiburg’s geological and human story.
The Oberer Steinbruch, located near Fuchsköpfle east of Freiburg-Herdern, is one of two quarries in the area. Here, a dark, layered amphibolite rock was extracted. This tough stone primarily served a practical purpose. It was used for road construction, contributing to the infrastructure of the region. The amphibolite itself is a fascinating geological formation. It exists as lens-shaped bodies nestled among the gneiss of the Black Forest. Its resilience to weathering has shaped the landscape. It’s responsible for the prominent ridges and hills that define the area. The very stone tells a story of volcanic activity and metamorphic transformation spanning millions of years. Imagine molten rock surging upwards between 480 and 440 million years ago. Picture the immense pressure and heat deep within the earth, transforming these volcanic rocks into the amphibolite we see today. This metamorphic process also created the surrounding paragneiss, the predominant rock type in this part of the Black Forest.
The Oberer Steinbruch, though now disused, still bears the marks of its working life. The south quarry face remains remarkably well-preserved. A 50-meter-deep gash in the hillside reveals steeply inclined fissures. These natural cracks and the layered structure of the amphibolite offer a visual testament to the forces that shaped this landscape. The quarry’s dark, greenish-gray amphibolite also contains coarser-grained quartz-feldspar rocks. These pegmatites and gangue granites are studded with large biotite crystals. Some of these even form ribbon-like patterns, adding an artistic flair to the rugged quarry walls. For mineral collectors, the Oberer Steinbruch once held an additional allure. It was known for prehnite, datolite, and rutile. The amphibolite here also contains garnet, often found as fractured, rounded grains. These hidden treasures hint at the complex mineral composition of this unassuming rock.
The Oberer Steinbruch is more than just a hole in the ground. It’s a window into Freiburg’s past, a testament to the interplay of geology and human endeavor. It’s a place where the earth’s ancient history is etched in stone. And the echoes of quarrymen resonate through the stillness.