||Opium is a black sticky tar which is the latex (sap) of the opium poppy. It contains over a dozen drugs, with the main ones being morphine, codeine, thebaine and papaverine. These chemicals don't all work the same way. Thebaine, for example, is primarily a stimulant.|
Heroin is not a natural chemical. It is a synthetic chemical made from morphine. Its effects are similar to the effects of morphine, only stronger. The effects of both heroin and morphine are quite different from natural opium, because of the mix of chemicals found in natural opium.
Red rock is not opium at all, and contains no known psychoactive drugs. It is actually an incense. For more on this, see the Red Rock Opium Myth.