The Crystal Mountain is situated between the Baharyia Oasis and the Farafra Oasis, in the White Desert’s North. Despite its name, the Crystal Mountain is rather a ridge, a rock or a hill sparkling like a crystal.
The arch is natural and small and is situated in the centre of the structure.
There are well-exposed caves and paleokarst topography developed within the Maastrichtian Khoman chalk. The paleokarst topography comprises huge collapsed breccias and paleocaves with columnar-shaped stalagmites. The collapsed breccias are composed of meter-sized rounded chalky limestone blocks within the massive Khoman Chalk, The outer surface of the breccias are surrounded concentric layers of stratified and centimeter-sized and triagonal clean calcite crystals. Black to dark brown impurities occur between and along the crystal boundaries.
The paleocaves are composed rimmed with the calcite crystals. The caves seems to be developed around the brecciated blocks that later on dissolved leaving concentric layers of secondary coarse crystalline calcite around the leached blocks. Some of these caves are filled with laminated reddish colored clay, silt and coarse sand of channel origin (cave floor fill).
The caves were probably produced by episodes of subaerial exposure during multiple exposure events known from Maastrichtian through Oligocene time. The paleoclimate during this period in Egypt was considerably wetter, with monsoonal and even tropical rain forest climates during the late Eocene and Oligocene (Bown and Kraus, 1988).