I think it would be beneficial for everyone if there would be a general consensus/guideline of selling gems through market NPC.
My suggestion is to use Miner Hammer (common weapon), socket monster gem, enhance it to +1 and put it on the market for whatever price you want for the monster gem.
That way players can easily filter by weapon type/name and/or enhance level to not go through all the junk.
I’m aware there will be quite a few scammer attempts, so paying attention is crucial but that applies to every inter-player interaction in almost any game.