One can be found in the wilds of Solstheim. It is located east of Bloodskal Barrow and north of Raven Rock. If lines are drawn in those directions it is exactly at the intersection of those two, near a Gold Ore Vein. Oddly, there are two Emerald Geodes located here, but mining one acts as though both were mined.
Two more can be found south of the Abandoned Lodge along with a dead miner and more Gold Ore veins.