In the patch notes it says that forest mangler yields a +25% gathering time bonus gem, while all the other artifacts that yield gathering time bonuses produce a jewel. Is that accurate and intended? It seems like the gathering time bonuses being gems and meticulous being jewels is the way it's intended.
Anything salvaged from a chest piece or a held item (weapon, shield), will extract as a gem, meanwhile anything extracted from anything else will extract as a jewel, that is the intended mechanic.
I would hope that we get additional gathering artis that provide the not only the "missing" bonuses, but that they are also on the opposite type of socket. That is, if the current speed bonus comes from a gem, the corresponding meticulous bonus comes from a jewel, or vice versa. Though, this is already broken, as mining speed (Gauntlets of Lead) and mining meticulous (BMC Ring) are both already jewels.