The "Crystal Mountain" in Egypt
A subvolcanic vault, filled with crystals of a hydrothermal event

Norbert Brügge, Germany

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.

It 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 Barite crastals (BaSO4) and/or Calcite crystals (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.
At first glance, the crystals of calcite and quartz are very similar, but a closer look reveals the differences.Quartz crystals have six sides, mostly with a pyramid-shaped crystal tip.The crystals of Calcite, on the other hand, can be rhombohedral (crystal with six rhombus-shaped sides) or scalalenohedral (triangles with different lengths and with different numbers of sides).
Every specialist will confirm that they are not quartz crystals what we see.

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 grow in cavities. It were also formed columns or domes with crystals within.
  • The hydrovolcanic origin of the solutions is confirmed by its hight mobility and incorporation of colored trace components:


Occurense of Baryte Mineralization in Bahariya Depression, Western Desert, Egypt
Y. S. Haroun &, M. F. Raslan (2009)

"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 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 late Pleistocene
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."


My comment:
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).



Photo Gallery

Crystal Mountain vault

Anthracite ? at the right side of the "archway"

"Archway" with firmly baked crystal structure

Brecciated limestone of Khoman Formation

Turbulent shapes

To anthracite transformed coal seam ?

Inserted brownish ferruginous strata

Breccia above ferrugineous strate

Crystal growth in ferruginous substrate


Crystal columns in a cavity

Hydrovolcanic formed columnar crystal structures

Crystal columns

Ferruginous substrate with crystal inclusions

Calcite crystals with the typical tips of rhombohedral crystal sides


Further hydrovolcanic structures in the environment of the Crystal Mountain



  Crystals also on hydrovolvanic fissures in the White Desert !

Fissure with erected limestone in the White Desert

Crystals on a fissure in the White Desert