Oolong Tea, as Wikipedia says: is a traditional semi-oxidized Chinese tea produced through a process including withering the plant under strong sun and oxidation before curling and twisting. Most oolong teas, especially those of fine quality, involve unique tea plant cultivars that are exclusively used for particular varieties. The degree of oxidation, which varies according to the chosen duration of time before firing, can range from 8 to 85%, depending on the variety and production style.

Yeah, what they said.