I was leveling up JC, and started Prospecting Thorium Ore, and noticed that it can make a nice amount of income.
Thorium Ore sells for about 20-25g a stack, and has chances to drop Thorium Ore - Items - World of Warcraft
Star Rubys, Huge Emeralds, Blue Sapphires, Large Opals, and Azerothian Diamond which sell for 10g+ each, and the Azero Diamonds sell for 20g+
So you have 4chances to get at least 40g, so
40g - 25g = 15g for doing nothing, you'll make more if you buy stacks for lower amounts.