Fullerites, or Polymerized Single Walled NanoTubules (P-SWNT) are very hard like diamond, but because the nanotubules intertwine they don't have the corresponding crystal lattice that makes it possible to cut diamonds neatly. This means impact is spread out throughout the material making it less brittle. Nanotubules are still very expensive to produce and so uses for a material lighter and stronger than steel will have to wait until nanotubule production becomes more economical.
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