Curiosity rover cracked open a Martian rock, revealing a sight never before seen on Mars - a dazzling display of yellow ...

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 ...

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 ...