torchlight-2
According to the splash screen
Don't save your Ember for later! Use them in any piece of equipment
with an open Socket. You will find better varieties soon, and the
ancient art of combining gems to make better ones has been lost in
this era.
Does this mean that I can combine gems already socketed with out losing the gem or the item? This just seems like bad advice from the game.
You need to find a transmuter in a dungeon first. You will find him while playing Act II and he will be standing around in the towncenter after that.
You can combine 3 gems to get a random new one. There is no upleveling of the gems anymore like in TL1, as far as I can see. I am far into Act II, close to Act III.
You can also combine any Item with 2 random gems of same level or higher to create a new socket in that item, additional to enchanting.
Here is the item without the specks:
And here is the item with the specks:
The difference in sell price is 110 Gold, which (correct me on this) is the sell price of the specks combined.
Best Answer
It's the game's subtle way of saying you can't combine gems anymore. You will find more gems as you play and they will become more powerful as you progress. You can't combine gems to make better gems.
You can't combine gems that are already socketed. Socketed gems are locked into the gear you put it into. You can either choose to recover the gem or recover the gear from a vendor in town.