The "Crystal Mountain" in Egypt
A subvolcanic vault, filled with crystals of a hydrothermal event
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 speleothems.
It is a subvolcanic vault, which was emerged probably during the Oligocene
age. The visible layers are limestones of the Khoman Fm.*
(Late Cretaceous age), as well as included a coal seam and reddish
to brownish ferruginous layers above. The strata are broken or
brecciated and intensely with each other folded. It is to be
ascertained intense heat. The coal seam 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.
Chalk Formation (Maastrichtian)
is represented by distinctive snow-white chalk and chalky limestones
with abundant chert bands and thin shale beds at top. 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
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 interfaces. The crystals are transparent to translucent and
are generally present in the form of angular to subangular shape."
|Travertine from Egypt's Western Desert: a terrestrial
record of North African paleohydrology and paleoclimate during the
Gloria Jiminez -- M.S., Earth and Planetary Sciences, University
of New Mexico, 2014
"The Crystal Mountain exhibits fluvial barrage and
perched springline facies, including pourover dams, microterracettes,
and dissolution caves. Much of the travertine at Crystal Mountain
showed evidence of recrystallization, with abundant sparite textures.
We note that the lack of vegetative facies at Crystal Mountain
could suggest high-temperature deposition, but further study would
be required to confirm this. Previous attempts to date travertine
at Crystal Mountain (Holzkamper, 2004) yielded ages out of U/Th
range. We have obtained the first date on Crystal Mountain travertine,
of 523 ± 30 ka on a groundwater speleothem-type structure, which
is interpreted to be the youngest carbonate in this deposit. Our
date of 523 ± 30 ka comes from the stratigraphically youngest unit
we observed at Crystal Mountain, and δ 234U model ages suggest greater
deposition earlier in the Pleistocene.
Finally, at Crystal Mountain, samples form two groups; one, with
groundwater speleothem-type samples, has similar δ13C values to
Kharga and Kurkur areas.The other group of Crystal Mountain samples
includes perched springline facies that may have been deposited
at high temperatures, and these have extremely depleted δ13C
values of -8 to -11‰. Given the lack of vegetated textures in Crystal
Mountain travertine, as well as the possibility of hydrothermal
deposition at that site, it is doubtful that the isotopically light
d13C at Crystal Mountain originated from vegetation."
That are marine limestones and belongs to the Khoman
formation, it is not travertine. The age determination data at speleothems
are not applicable for the origin of the Crystal Mountain (included
the primary mineralization).