Prospecting is a Jewelcrafter ability that allows them to turn a stack of five raw ore into precious gems. Only common ores (not green-quality or quest ores) can be prospected. Note that, unlike disenchanting, you cannot gain skill from prospecting.
Prospecting ore will always result in some type of powder and a green-quality, sometimes 2, gem. There is also a chance to obtain an additional green-quality gem, or a blue-quality gem from ore in Outland. The type of gem obtained always includes what can be mined from a node of that ore, with the exception that prospecting Thorium Ore will not result in an Arcane Crystal.