Types/stages of Heroin:
Type #1: Opium
Type #2: Morphine base/HCL
Type #3: Heroin base (most suitable for smoking, the Afghan heroin on the European market which needs to be heated a bit with citric acid before injection is this type)
Type #4: Heroin HCL (white heroin)
It is rare to encounter type #1 and #2 in the heroin market because they are not heroin.
Black tar heroin does not fit in here as it is uses a different method altogether to get from opium to heroin. This method does not utilize acetic anhydride (which is watched and hard to get) but regular acetic acid. It is easier, cruder. The product is not just heroin, but also 6-MAM and 3-MAM. 6-MAM is more potent than heroin and 3-MAM is less potent than heroin. Toxicity of its metabolites are not fully certain.