I think with Cataclysm many people have forgotten about the older ores and what each ore can contain. Thorium Ore prices for me have steadily been floating around the 30g to 40g a stack. If you prospect Thorium ore according to enchantrix you have the below chances to get these gems.
30% Huge Emerald
30% Azerothian Diamond
30% Large Opal
30% Blue Sapphire
10% Star Ruby
Gem prices range from 5g to 15g and you can get on average 6 per stack of ore. I also found as a Jewelctafter I could make a number of rings and disenchant them.
These have a chance to disenchant into Illusion Dust, Greater Eternal Essences, Large Brilliant Shards (Greater Eternal Essences usually fetch between 40-60g each)