February 24, 2020
The "Crystal Mountain" in Egypt
A subvolcanic vault, filled with crystals of a hydrothermal event
Norbert Brügge, Germany
(I have taken the liberty to edit this essay for syntax and punctuation. jp)
The crystals from the Crystal Mountain between the Bahariya Oasis and Farafra Oasis, in the northern section of the White Desert, are not Quartz crystals. They are Barite crystals (BaSO4) and/or Calcite crystals (CaCO3).
To ascertain the hardness of the crystals, 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 cannot.
At first glance, the crystals of Calcite and Quartz are 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 scalenohedral (triangles with different lengths and with different numbers of sides). Every specialist will confirm that what we see here are not Quartz crystals.