I quote this from the eqtinkers mailing list...

<snip>
Okie, take this with a grain of salt, becasue I haven't verified it..

Talking to an enchanter friend of mine over the water-cooler at work, and
he gave me the following info about a gemcutter that he borrowed.

Take one gem (he was using rubies), with it in the cursor right click on
the gemcutter.
The gem should now be "A fine ruby" (or whatever)
Combine the fine ruby as you would any other gem + metal ( he was making
plat ruby veils)
Aparently the fine gems make the same items as the regular one, but have a
lower trivial and therefore higher success rate..

Should be easy enough to verify, as it's not destructive and doesnt involve
combing the gemcutter with anything, and you can always try with a cheap
gem.. Anyone got one in the bank?

<snip>

Time to go and support your friendly neighborhood tinker, me thinks :)

Cogg - RZ
Master tinker/jeweler/brewer/beggar/enchanter