It was Raeth's gem I was talking about, and it's location really is iffy. Probably doesn't matter all that much though.
Are the Aethers situated on the bearers' hands for practical reasons like: easy to mentalize attacks from arms, easy to access, the body part most likely to come in contact with the Aether source as, well, we use our hands to grab things, or are there more Realmatic reasons for this? Hmm... Probably the former..