Ontario Mineral - Graphite


Rocks minerals Ontario Graphite

C, Elemental Carbon
Native Elements
for the lead in pencils, as a toughener of steel and as a lubricant.
black silver
metallic to dull
crystals are opaque
Crystal System:
hexagonal; 6/m 2/m 2/m
Crystal Habits:
massive lamellar veins and earthy masses. also as scaly granules in metamorphic rocks.
perfect in one direction
1 - 2
Specific Gravity:
2.2 (well below average)
black gray to brownish gray
Other Characteristics:
thin flakes are flexible but inelastic, mineral can leave black marks on hands and paper, weakly conducts electricity.
Associated Minerals:
quartz, calcite, micas, iron meteorites and tourmalines.
Local Occurance:
Goulding-Keene Quarry, Saranac Mine
Best Field Indicators:
softness, luster, density and streak greasy feel; stains fingers.


Graphite is a polymorph of the element carbon. diamond is another polymorph. The two share the same chemistry, carbon, but have very different structures and very different properties. Diamond is hardest mineral known to man, Graphite is one of the softest.
Diamond is an excellent electrical insulator, Graphite is a good conductor of electricity.
Diamond is the ultimate abrasive, Graphite is a very good lubricant.
Diamond is usually transparent, Graphite is opaque.
Diamond crystallizes in the Isometric system and graphite crystallizes in the hexagonal system.
Somewhat of a surprise is that at surface temperatures and pressures, Graphite is the stable form of carbon. In fact, all diamonds at or near the surface of the Earth are currently undergoing a transformation into Graphite. This reaction, fortunately, is extremely slow.
All of the differences between graphite and diamond are the result of the difference in their respective structures. Graphite has a sheet like structure where the atoms all lie in a plane and are only weakly bonded to the graphite sheets above and below. Diamond has a framework structure where the carbon atoms are bonded to other carbon atoms in three dimensions as opposed to two in graphite. 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.