Hello and Welcome to HCM,
Thanks for writing to us.
When you eat things that are not meant for human consumption, you have a condition called PICA
. Chalk is not harmful in the sense that it can poison you. Because of it's consistency, however residue is easily ingested into the lungs and could possibly cause pulmonary distress
If you find yourself wanting to ingest such things as chalk, talcum powder, etc. you are suffering from a mineral deficiency
. You should have a complete medical evaluation. this is easily treated, so do see a doctor soon.
Hope this helps you.
Wishing you good health...