The Crystal Mountain is an obligatory stop for adventurous safari tours in the Oases of Egypt in the White desert. A small natural arch in the rock and the glittering calcite crystal walls make it a perfect place to pose for photos. This is what geologists call an exhumed cave, a cave complete with stalagmites and stalactites that has been thrust upwards by earth movement and with time has lost its roof to erosion and has almost weathered away. The calcite crystal developed in paleo caves of khoman chalk.
The crystal mountain stands on the very edge of the of the White Desert, and soon the black iron and basalt pebbles give way to the sand-blown chalk formations which loom on either side of the road.
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 (after 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.