From the WoWPedia page :
Stormjewel is an epic gem that can be found by fishermen when doing Dalaran daily fishing quests. They can either be found in a Bag of Fishing Treasures, or the treasure bag can contain a Tiny Titanium Lockbox which in turn can contain a stormjewel.
Prior to patch 3.2, they were the only Northrend epic gems availabe to non-Jewelcrafters. They provide identical bonuses to the "ordinary" epic gems added in that patch.
Toward the end of
Blizzard have also done nothing but nerf the gold to be made from mining+prospecting since Cata was released.
As a gold community, we overhype some things. Remember that there was going to be unlimited demand for Dream Emerald for all those hunter scopes? I'm still sitting on a large stockpile, with nowhere to sell them.
Back before 4.2, I (correctly) predicted that I thought that 4.2 would not introduce Epic gems. For the reasons outlined (i.e. it is a stealth nerf to older content), I now think that at some stage in 4.3, we will see new epic gems. It may not be during the initial release, as leading PVE guild's don't need them initially, but middle of the road guilds will.
It is just as likely that alternate methods of getting Epic gems (Honor, Justice or Valor points; fishing) will limit the initial windfall of prospecting Epic gems.
I will still do my JC dailies. I will stockpile a relatively small amount of pyrite ore.
I am uncomfortable gambling my fortune on fools gold.