Auf dem Stein quarry, Suttrop, Warstein, Sauerland, North Rhine-Westphalia, Germany
Suttrop-Type Quartz
The "type locality" of these crystals is "Auf der Vogelstange", a street at Suttrop, where crystals could be found until the area was mostly overbuilt. They can also be found in nearby quarries.
Similar quartz specimen can be found along a "belt" of Devonian and Carboniferous limestones at the northern end of the Sauerland, a low mountain range in Nordrhein-Westfalen, Germany. This belt extends over 150 km from Dornap near Wuppertal in the West to Wünneberg-Bleiwäsche south of Paderborn in the East and is about 20 km wide.
Among the many other locations where Suttrop-type quartz can be found are quarries at Kallenhardt, Wünnenberg-Bleiwäsche, Warstein, Hagen-Hohenlimburg, Velbert-Rhodenhaus.
The crystals themselves are younger than the Devonian limestones and formed probably during the late Paleocoic age in a hydrothermal environment.
The crystals can be up to 5cm long, but most are much smaller. The color of the translucent crystals is most commonly a creamy white to light brown. The crystals are characterized by a pseudohexagonal, double terminated habit and a zonar inner structure. Both geyser-like rhythmic movements of water and tectonic events have been discussed as a cause of the zonar pattern. The mineral anhydrite, CaSO4, was incorporated at relatively high temperatures; later some of it was dissolved at lower temperatures (anhydrite is more soluble at lower temperatures), leaving tiny cavities in the crystal that contribute to its white color. Interestingly, overall the temperature during crystal growth increased with time, starting at about 60-80°C and ending at above 120°C, perhaps even above 300°C (Behr et al., 1979), which is very different from the typical development of quartz from Alpine-type fissures, for example. The crystals have a very high number of fluid inclusions, consuming up to 10% of their volume. Accordingly, the crystals have a lower specific gravity than usual. They also never show any accessorial faces and are heavily twinned.
While single double-terminated crystals are most sought-after, the crystals usually occur in irregularly intergrown aggregates that may weigh many kilograms and sometimes accumulate in former karst cavities.
Edited 1 time(s). Last edit at 03/28/2009 10:26AM by Amir C. Akhavan.
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