Graphite, Graphite would melt at 4000C (a bit higher than irl) and would be a non flammable solid with highly insulative properties, but would become PGRT at pressures of >5 and it would conduct electricity (rest of post is optional) PGRT will become GRPE (Graphene) at pressures of ≥90 and temperature of 900C and while sparked, Graphene would melt at 4500C (unrealistic) and would block all pressure and conduct THROUGH INSL at speeds twice that of GOLD/PTNM