Ruby in Zoisite Locality: Longido, Arusha, Tanzania Description: Superb hexagonal ruby crystal, the red-pink gem variety of the mineral species corundum, in green zoisite matrix. The ruby crystal has exceptionally rich color and runs comple
Quartz crystal/agate cylinder / There are two main groups of quartz: chert and chalcedony. Agates form in cavities left by gas bubbles in cooling lava. Silica-rich groundwater builds layers of crystals on the cavity walls.