There's a big difference between having an edge that never gets dull, and a blade which will never chip or snap. Hard substances which hold a very sharp edge over time also tend to be extremely brittle. If you had a sword with the same dimensions as a steel sword, but it was made of diamond, then the edge could be ludicrously sharp, but the blade might snap in the middle if you tried to cut through someone with it and struck bone, misaligned the edge, etc. Despite that, if you only used it to slice vegetables in your kitchen with careful technique, it might stay wicked sharp for a hundred years. I can only assume that's what they had in mind, and they didn't explain it properly.
Edited by TheBigBopper
Is the Subtle Knife from His Dark Materials monomolecular or monatomic? It keeps getting added to the page, but no one has posted its width.
If it doesn't have a specified width in-universe, then it doesn't belong on this page.
In the Real Life section, diamond blades are said to last forever, but also break after cutting human flesh. Which is it?
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