They do burn, but not easily. They only seem to char slightly with an oxy acetylene torch (I assume that's what is being used here) https://www.youtube.com/watc

They do burn, but not easily. They only seem to char slightly with an oxy acetylene torch (I assume that's what is being used here) https://www.youtube.com/watch?v=hF_yqriai7E https://www.youtube.com/watch?v=hF_yqriai7E It might be a heatsinking thing, as diamond does transfer heat well, and the metal underneath would continue to carry it away.