Concerning concave facetting

[C.Sanwill]

Hello,

I haven't posted here for a while but I had a small question. I tried concave faceting for the first time and, well I found it hard to be precise despite having cut stones beforehand.

The machinery is by all means superior in terms of precision, but the rigidity of switching the mast and finding back decent positioning is hard.. I was used to a Raytech machine, which I has served me well. I am by no means a professional but I managed to do good stones quality wise, although I am bit slow.

I also noticed that concave facets tend to take quite a bit of time to be polished. Is this due to the chemical arrangement of the materials? I know of differential hardness, but I was wondering how these apply to concave facetting...