Question

Advantages and disadvantages of eating slate pencil

Answer 1

Modern pencils don't contain lead anymore -- they contain graphite -- a pure carbon that, while messy, is harmless in the amount contained in a pencil.

Answer 2

Slate pencils contains calcium carbonate and it may be harmful when it is taken in excessive amount,then it may cause stone formation in kidneys.

The continuous craving for eating inedible substances (like chalk, slate pencils etc) is known as Pica.

It is one of the features of Iron deficiency anemia.

but it is not very harmful if taking in small amount.
hope this helps :)