The carbon-carbon bonds in both minerals are actually quite strong, but it is the application of those bonds that make the difference. Graphite can only be confused with the mineral molybdenite which is metallic bluish silver in color. However, molybdenite is much denser and has a silver blue streak. Most graphite is produced through the metamorphism of organic material in rocks. Even coal is occassionally metamorphosed into graphite.
Some graphite is found in igneous rocks and also as nodules inside of iron meteorites.
Color is black silver. Luster is metallic to dull. Crystal Habits include massive lamellar veins and earthy masses. Cleavage is perfect in one direction. Fracture is flaky.