The thermal conductivity of pyrolytic graphite parallel to the layers is in the 400-1700 W/m-K range at room T, compared to 10-50 W/m-K for steel.  Hold the edge of a piece of graphite and a piece of steel of about equal size against an ice cube.  The graphite conducts the heat from your hand better and penetrates farther into the ice in the same amount of time.

The pyrolytic graphite is thin and brittle and bits of it tend to break off in the ice.