Chalk of Indelible Authorship

Wondrous item (chalk stick), rare

This chalk was carved out of the floating globes of sedimented sea creatures in the plane of water. 

When you write something with this chalk it never vanishes. It writes cleanly and smoothly in any environment on any surface. 

Spells requiring chalk can use this chalk for half of their required gold cost. Their duration is doubled if cast with this chalk. The actual chalk drawn during spellcasting will remain forever. Casting the same spell in the same place requires half the normal casting time.