Roman "technological" tools

[jvrjenivs]

Hi guys,
very interesting the "gem carving " post, thanks.
Time ago I read that the Romans could do a lot of work with diamond dust applied on a common iron. They knew a lot of tools and probably many were lost, but I think they need a magnifying glass. What knowledge they had about this? They worked very well on glass, but could make a very good lens?

As far as I know magnifying glass was first introduced in the arabic world in the 7th century, but I'm not sure about that. At least I know about no reference to anything like in in Roman sources. But as I said, a trained eye (from a child) can do a wonderfull job.