Graphite, is made of Carbon atoms linked together by covalent bonds. One of its uses is that it is used in making crucibles that can withstand very high
temperatures, and hence can be used to melt substances with a very high melting point. But, according to the properties of covalency, molecules or compounds with covalent bonds have a low melting point. So shouldn't the crucible itself melt before the substance melts? Please explain.