Natural calcium carbonate from France. Chalk is usually used for making gesso and absorbent grounds for painting. A small amount of chalk can be added as an extender/filler for a pigment that is very high tinting.
Chalk is also helpful for cleaning up a your palette. Using a paper towel or small cloth, scrub a soft paste made with a bit of chalk and water to remove stubborn pigments and wet paint from your work surface.
