Crystals are mineral formations that have a regular, geometric structure. They commonly form when minerals are melted by a heat source such as a volcano and then slowly cool down, allowing the atoms to rearrange into orderly patterns. They also form when mineral-rich water evaporates, leaving the crystallized minerals behind. One of the commonly found crystals is quartz, which gives off sparks when struck together (visible in the dark). With the exception of rare and unique specimens, most crystals have little or no value.
Quartz is common around volcanic vents. Examples are in the Mujib Dam area, and south of Karak around the GPS coordinates: 30.9658°, 35.7250°. Crystals on the surface of boulders are also found in the valley of Wadi al-Seer, at the GPS coordinates: 31.8831°, 35.7550°. Gypsum crystals are common in Wadi Dahek, southeast of Azraq, around the GPS coordinates: 31.5700°, 37.1217°.