[unclepresent]

chisel made from steel may be but even then... try it on concrete or rock just for experiment (I tried).

But if chisel is made from cooper or iron ... good luck ... may be you have 10000 years in your life

[pvg]

This particular sarcophagus is from Ptolemaic-period Egypt, they had iron. But they managed to carve granite (and a bunch of other softer stones) before that, with copper and other tools. Not all of the techniques are known but a big part of the answer is that (unlike you!) they put long, sustained, organized effort into it'.