First off what does life "need?" (ie what is it missing that other elements have)
-Permanent control
-Creature control
-Card Draw acceleration
-A weapon that has more damage
Second, what concepts "fit" with life (note that none of the above really "fit")
-Healing (but not max hp gain)
-Speed
-Low to Medium hp creatures
-Heavy reliance on creatures for damage(not permanents or spells)
-Poison
-Benefits derived from having creatures (feral bond-esque stuff)
-Plant based concepts
-Quanta conversion (based on how plants work, ie rustler and forest spirit)
-Simplicity
With those in mind, any Control should at best be "soft". Life is more about healing and positive things (with then notable exception of poison).
With that out of the way, do you mind if I make some suggestions?
I know you are doing the gem series, so of course it will remain a gemstone, the question is what it should do.
A brief read of Wikipedia on Emeralds told me they are fragile. I also found the story about Cortez engraving the beautiful emerald he found in Latin America and Brantome thinking that it was affront to nature interesting. Brantome blamed the engraving for the death of the King of France among other things.
That kind of suggests that maybe destroying this card would somehow hurt the opponent. Perhaps if it was a permanent, destroying it would result in -10 hp, or 5 poison counters or something along those lines.
As far as the ability, Emeralds are the stone of love, so maybe something based on "love" would be nice. Perhaps It could buff creatures that are directly next to it? Or if it was a permanent it would choose one (random?)creature to buff until it was destroyed.
The other direction you might take is to change the stone to Jade. Jade is the symbol of wealth and nobility in China and so what immediately comes to mind for me is a permanent that increases your electrum winnings at the end of a game. Seems kind of useless in game but it would be a completely new concept and would probably end up in a lot of grinding decks. Maybe something like +25% electrum per played Jade Stone. Just a thought.
Good luck remaking, I hope what I said was somewhat helpful.
