The 75-year-old letter was written by a coal miner who said that this mineral was mined at that time from a site in Germany.

With no disturbances, the crystals kept growing, eventually reaching gigantic sizes. It’s like making rock candy, but instead of days or weeks, these crystals took thousands of years to grow to ...

An image of the rock shows crushed material with yellow crystals, like a geode that’s been smooshed. If you’re reaching to pinch your nose against the rotten-egg smell, don’t worry.

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 ...