chalk

powders to the touch. leaves a mark on anything dark. composed, almost entirely, of creatures that had names and shells and brief careers in the warm shallows of a sea no map you own remembers.

kept beside the flint it once hosted in its bed. used at the kitchen threshold to draw a line a child later argued with. a useful thing to put in a pocket if you mean to leave a path through a long forest.

writes on stone but not on the marble. writes on the obsidian beautifully.