The "Crystal Mountain" in Egypt
A subvolcanic vault, filled with crystals of a hydrothermal event
last update: 28.05.2010
should once be put right, that the crystals from 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 probably Barite (Schwerspat,
BaSO4) and/or Calcite crystals (Kalkspat, CaCO3), which to ascertain at the
hardness of the crystals easily. Quartz (SiO2) has the hardness 7, Barite
and Calcite the hardness 3.5-3.0 (Mohs-scale). Quartz crystal can scratch
glass, Barite or 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 was emerged probably during 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 impregnated 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 crystals have increased out of climbed hydrovolcanic solutions.
The hot solutions were high concentrated with BaSO4 and/or CaCO3, which had
been solved from the sediments. The solutions have penetrated into all cavities.
After cooling of the solutions the crystals could increase. It were formed
columns or round domes with crystals within.
* 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.
"High grade Barite mineralization is
found mainly in the form of different veins restricted to the ground surface
of Bahariya depression. The barite veins trend in different directions and
are actually associated with the major folds and faults that are restricted
to the oldest rocks of Sabaya Formation which form the floor of the depression.
The latter occurs within a major northeast trending belt of considerable extension
about 100 km long and 40 km wide. Several other folds of the same or later
tectonic phase but of lesser extension occur parallel to or perpendicular
to the main anticlinal trend.
The Barite veins are widely distributed to the south of Gebel El Hafhuf which
is composed of a rock sequence including sandstone, shale, limestone, phosphatic
limestone and phosphatic calcareous sandstone. This succession is capped by
the Oligo-Miocene basaltic sheet which takes the form of open circle of about
20 m thickness.
The barite veins are restricted to the fractures that are parallel to the
main E-W or NW-SE striking faults in the Sabaya Formation. These veins occur
subparallel sets with more than 7 m length and ranging in width between 0.5
to 4 m. These veins are numerous and distributed in association with tectonically
formed fractures and fissures.
Barium was leached from the basaltic extrusion during high temperature circulation.
Tertiary Oligocene basalt at Gebel El Hafhuf, Bahariya Oasis is related to
continental intraplate volcanism. Fumarolic and geyser activities belong to
Oligocene period were consider as gas maar resulting from a phreatic explosion.
Release of sulphate fluids from the sulphate-rich minerals involved in the
Brine deposits distributed within Bahariya Depression at the Quaternary, namely
polyhalite, kieserite and kyanite.
Migration of these fluids through the deformed strata followed by barite mineralization
as a result of a rapid primary precipitation at or above the sediment / fluid
The crystals are transparent to translucent and are generally present in the
form of angular to subangular shape."