Mighty Alchemist Stone

Definetly an upgrade to its lvl 70 predecessor, although its a shame that its "only" lvl 75 required. Chances are high that at level 80 it will eventually be replaced by other trinkets whereas I considered the lvl 70 versions definetly amongst the best obtainable trinkets as a casual player.

Nonetheless, the 40% bonus for healing/mana potions is not to be underestimated and can be of high value wether your main goal is PVE Raid/Solo or PVP. Nothing is more satisfying then getting a 6000+ crit from a healing potion when at 10% HP :)

Worth noting is that it seems to be fairly cheap to craft, and it can also be used as a philosophers stone, just like all the pre-WotLK versions, while this one itself doesnt seem to require one to be crafted

Can you equip two of them or is there some kind of rule?

*Updated for 6.1* - Philosopher's and Alchemist's Stones over the years

Vanilla

BC

Wrath

Cata

MoP

WoD

Philosopher's Stone

Alchemist Stone
Assassin's Alchemist Stone
Guardian's Alchemist Stone
Redeemer's Alchemist Stone
Sorcerer's Alchemist Stone

Indestructible Alchemist Stone
Mercurial Alchemist Stone
Mighty Alchemist Stone

Lifebound Alchemist Stone
Quicksilver Alchemist Stone
Vibrant Alchemist Stone
Volatile Alchemist Stone

Zen Alchemist Stone

Draenic Philosopher's Stone
-New for 6.1-
Stone of Wind
Stone of the Earth
Stone of the Waters
Stone of Fire

Remember, you need one of these to be either equipped or in your bag to do transmutations. Enjoy!