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In Switzerland, granular and friable dolomite is most of all to be
found in the Piora Zone and in the Binn Valley. Since the middle of the
19th century, rare minerals have been exploited at the mine of
Lengenbach. Mineral lovers and geologists from all over Europe, most of
all, though, from Great Britain and Germany, have been thrilled by the
beauty and variety of the minerals from Lengenbach.
Picture: Raphael Ritz (1883): The mineralogist. On the table of the
crystal hunters lie numerous minerals from the Alps. The mineralogist
(probably J.J.G. vom Rath, Bonn) inspects a sugar-grainy dolomite with
realgar from the mine in Lengenbach.
Source: H. A. Stalder
et. al. (1978): Die Minerale des Binntales.- Jahrbuch 1975-1777 des
Naturhistorischen Museums der Burgergemeinde Bern.
Picture: Realgar with quartz on sugar-grainy dolomite (picture by P. Vollenweider)
Dolomite rock [calcium magnesium carbonate] is a typical trias sediment
in Switzerland, cropping out in the rocks of the Jura range and the
Alps. They were formed between 240 to 208 m years ago, when a shallow
tropical sea still dominated these landscapes. According to present-day
knowledge, dolomite is created through evaporative pumping in the
intertidal range or in closed basins, which are periodically flooded.
Dolomite can also emerge through microbiological activity.
The term granular and friable dolomite ('zuckerkörniger Dolomit')
refers to the structure of this variety of the mineral at the same time
as it describes the low cohesion of this rock. The low stability was
caused by static recrystalisation, during which isometric grains with
symmetrical grain boundaries came into existence.
Picture: granular and friable dolomite with pyrite veins (picture by F. Schenker)
from Dr. Franz Schenker, mineralogist and petrographer, Meggen, www.fsgeolog.ch
Specialist literature: www.nmbe.ch/deutsch/513_11.html
Pictures: www.vs-wallis.ch/wallis/goms/bin/lengenbach.html
Crystal hunting: www.binntal.ch/strahlern/mineralien.html |
