I've done diamond polishing (usually called cutting for some reason, but faceting is a better term) and I can assure you it has very little in common with lens shaping and polishing, which I've also done. On the other hand, in the distant past, semi-precious stones and even precious stones were often cut en cabochon, basically buffing up and rounding the existing shape. Diamond faceting and cutting are done in the one action after it is cleaved and bruted to rough shape - the facet is polished and cut in the same operation. Lenses on the other hand have to go through a sequence of coarse to fine grinding until the final polish which for the highest quality lenses is still done using rouge (actually cerium oxide now) with a pitch lap. Probably glass was ground to shape using garnet sand or emery. The lap could have been made from wood, probably the end grain - the sand would penetrate into the wood and protect it from wear to some extent. The Chinese jade "carvers" sometimes used wooden tools on their lathes. There is no real need for blacksmiths to be involved in lens making.

- Mike -