This Hexagonal Crystal (六角水晶, Rokkaku Suishō) was given to Koyuki Kazahana by her father as a child.
As its name implies, it is a hexagonal, purple crystalline stick with an indent at the bottom. The top has a key-hook with a string, making it a necklace.
Though Koyuki lost faith in her father's beliefs, she still kept the crystal with her. It was later revealed to be the key to a generator to turn the Land of Snow into the "Land of Spring". Kakashi had replaced it with a fake key, but Dotō found out the duplicity, and managed to procure the real one. Dotō incorrectly believed that it led to a great treasure, and sought to take the key for himself, only to be infuriated when he saw the truth behind it.