For those confused about the title, there's a joke that every moderator has a "diamond hammer" (diamond from the little by the username). In a chat discussion, it was brought to my attention that a diamond can burn (which makes total sense because it's pure carbon) after I got a notification in orange in the topbar of SE.

Anyway my question is why can something so durable be able to burn? I would imagine that there would be a relationship between flammability and durability, especially since metal cannot burn.* Is it just a coincidence that most people think hard == inflammable? Why can diamond burn?

*It can burn when oxidized IIRC.

  • $\begingroup$ It doesn't really surprise me, as diamond is pure carbon in a densely packed crystal lattice. By adding enough heat you'll release carbon atoms from the lattice, and when oxygen is present CO2 will form. It'll take a lot of heat though, I guess (that's why this is only a comment, not an answer, although I'd be glad to make it into one if you think it's sufficient). $\endgroup$
    – hugovdberg
    Apr 16 '14 at 21:16
  • $\begingroup$ This question appears to be more about the chemistry of diamonds than the "earth science" aspects of it. $\endgroup$
    – Tom Au
    Apr 17 '14 at 22:15
  • $\begingroup$ Yeah, this would definitely sit better at chemistry.stackexchange.com than here, it's got nothing to do anything geological, really. Also, I find the joke at the start kind of more distracting and confusing than funny, but maybe that's just me. $\endgroup$
    – naught101
    Apr 18 '14 at 1:15
  • 3
    $\begingroup$ This question appears to be off-topic because it is about chemistry $\endgroup$
    – naught101
    Apr 18 '14 at 1:15
  • 1
    $\begingroup$ The real question here is why would anyone waste a diamond by burning it? $\endgroup$
    – f.thorpe
    Jul 7 '14 at 7:05

It is bond strength, not hardness, that determines how easily oxygen can attack and burn a material, allowing me to burn a diamond in a pool of liquid oxygen resting in a block of graphite.

Diamond is hard because its bonds form an inflexible, three-dimensional lattice. However, the strength of these bonds themselves is not even as strong as graphite, for example. Graphite has much stronger bonds, but they create "sheets," which can slide around, making graphite softer but harder to burn.


Indeed, people have burned diamonds before by putting them in tubes of pure oxygen.


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