|hardness||Graphite is one of the softest materials.||Diamond is one of the hardest materials.||The crystal structures and the bonds between the carbon atoms are different.|
|crystalstructure||Synthetic graphite only comes in the hexagonal alpha- Modification before (honeycomb flat C-layers in ABAB order).|
In natural graphite deposits can be up to 30% in the rhombic beta-Modification is present (honeycomb-shaped flat C-layers in ABCABC order).
Comparison of the two modifications: see below
The honeycomb layers are only very loosely bound to one another. The bond between the carbon atoms is strong within the layers.
|Natural and synthetic diamond crystallizes in the cubic system (cube, octahedron, etc.)|
There is a very strong bond between all carbon atoms.
|ABAB graphite grid:|
|colour||Only black fabric samples are known of graphite.||The color of diamonds varies from colorless, transparent through various shades to black, opaque, depending on the level of contamination.||The color is attributed to the different bonds between the carbon atoms in graphite (delocalized bond) and in diamonds (localized bond).|
|EnamelPoint||Graphite has no melting point, but becomes plastically deformable above 2500 ° C.||Diamond melts at 3800 to 4440 ° C (depending on the source) and a pressure between 127 bar and 130,000 bar. Under 127 bar it converts to graphite. ||So far, no satisfactory explanations are available.|
|density||The density for amorphous graphite varies from 1.8 to 2.1 g / cm3, for crystalline graphite from 1.9 to 2.3 g / cm3.||The density varies from 3.150 to 3.513 g / cm3. ||The density fluctuations are unusual and have not yet been explained satisfactorily.|
|The thermal conductivity of graphite is about as bad as manganese.||The thermal conductivity of diamond is very good (about two to five times greater than silver and five to eight times greater than gold).||There are completely different heat conduction mechanisms that are complicated to explain.|
|Polycrystalline graphite samples conduct electricity like metals (about 8 times worse than manganese - the least conductive metal).||Synthetic diamonds are semiconductors, natural diamonds are either very good insulators or strong electrical semiconductors.||The good conductivity of graphite is attributed to the bonding conditions within the honeycomb carbon planes. The conductivity of diamonds is not yet fully understood.|
|solubility||Graphite dissolves better than diamond in molten metal (especially iron, but also cobalt, nickel, chromium and platinum).||Diamond dissolves more poorly than graphite in molten metal (especially iron, but also cobalt, nickel, chromium and platinum).||The differences in solubility are not yet fully understood.|