Ok, I have what's called PICA. It's the craving for non-edible substances. Dirt, rocks, chalk,...earthy type things. I am 38 years old and I have been eating chalk since I was 14. My mouth literally waters when I think about chalk. Right now I have 4 boxes of different kinds of white chalk in my bathroom. I prefer the heavier more oily based chalk. I usually eat 2 pieces while I'm taking a bath. I start out with the heavier chalk and end with the more "chalky crumbly" chalk. People with PICA are usually deficient in a certain nutrient, particularly calcium. I do worry about what I could be doing to my insides but I swear I can't live without it. I love it. I love chalk.