There is a trick to getting this.
Orb of Alchemy requires a white/common item.
Jewels never drop as white, only blue/magic and above.
What you need to do is use an Orb of Scouring on a jewel to revert it to white/common, then you can use the Orb of Alchemy and hope for the best. Shouldn't take too many tries, there are certainly harder RNG achievements than this one.