The "Crystal Mountain" in Egypt
A subvolcanic vault, filled with crystals of a hydrothermal event
Norbert Brügge, Germany
Dipl.-Geol.
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should once be put right, that the crystals in the known Crystal Mountain (28°
26' E and 27° 39' N) between the oasis Bahariya and Farafra, northern of
the White Desert, are no quartz crystals. They are calcite crystals (Kalkspat,
CaO2), which to ascertain at the hardness of the crystals easily. Quartz (SiO2)
has the hardness 7, calcite the hardness 3 (after Mohs-scale). Quartz crystal
can scratch glass, calcite can it not. The origin of this Crystal Mountain is interesting. The hill was opened during works at the road from Farafra to Bahariya by chance and destroyed in part. The material was installed into the road. Today is the Crystal Mountain a popular stop for the tourists. Still more interesting is the geological context. The hill is not a paleokarst cave with columnar-shaped stalagmites. It is a subvolcanic vault, which has emerged probably in the Oligocene age. The visible layers are e.g. White Desert limestone of the Khoman Fm.* (Late Cretaceous age), as well as a younger coal seam and hydrothermal imprenated reddish to brownish ferruginous layers. The strata are broken or brecciated and intensely with each other folded. It is to be ascertained intense heat. The coal seam e.g. was transformed to anthracite. The calcite crystals have increased out of climbed hydrovolcanic solutions. The hot solutions were high concentrated with CaCO2, which had been solved from the white limestone. The solutions have penetrated into all cavities. After cooling of the solutions the crystals could increase. * The white limestone of the Khoman Formation is dated as middle to latest middle Maastrichtian (Gansserina gansseri and Contusotruncana contusa foraminiferal Zones). An open marine, warm Tethyan outer shelf environment of deposition is inferred. Not all of here used pictures are my property. I have copied them however in the interest of the generality from the Internet and with the hope, that the owners have for it understanding. |
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| Further hydrothermal structures in the environment of the Crystal Mountain | |
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| Calcite crystals also on hydrothermal fissures in the western White Desert ! | |
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