[capitan_refugio]

It has been a while since I cracked a crystalography book (+/- 25 years), but I'll take a stab at this.

I recall that the difference between graphite and diamond is in the arrangement of the carbon atoms and the strength of the carbon-carbon bonds. Diamond has a covalent bond; graphite has van der Waal bonds. I recognize "adamantine" as a description of "luster," so I'm not sure an "adamantine configuration" is. My Manual of Minerology does not go into enough detail.

Because of the carbon tetrahedrons in diamond, there is a lot of "open space" between the atoms. I think this accounts for diamond's cleavage. (Graphite, one the other hand, tends to be sheet-like.) So in diamond, the carbon bonds are strong, but as the crystaline structure is removed from the great pressures and temps of the mantle, the structure becomes unstable.

Sorry I don't have my crystalogrpahy book handy. It is out in the garage in a box somewhere.

[King Prout]

adamantine just means diamond-like
it is used casually to describe anything with properties of diamonds, usually hardness or duarability. cf: adamant

in this use, it is the valence configuration you call van der Waal bonds. This configuration is found in diamonds and boron-nitride(sp?) - a similarly hard and durable synthetic which has the additional property of not burning when used at high temp in an oxygenated atmosphere.

I'll have to take your word for the instability, though it goes against what little I recall of what I learned about that molecule.. been a long time since basic chemistry.