Evidence for the use of rock crystal - a rare type of perfectly transparent quartz which forms in large hexagonal gems - has occasionally been found at prehistoric sites in the British Isles, but ...
Large crystals found in geodes and other rocks are relatively rare. Pink ChalcedonyA pink chalcedony shows off its beauty. Chalcedonies include many types of cryptocrystalline quartz gems and ...
Curiosity found a field of similar light-toned ... the rover had crushed a similar-looking rock and revealed sulfur crystals. Curiosity is a rolling laboratory with drilling capabilities, but ...