Typically amphetamine "paste" is water-based, because amphetamine salts are deliquescent (absorb water from the air). What you smell may be amphetamine freebase, phenylacetone, or side products from the synthesis.
Realistically though, you can only guess, because there's no "standard" recipe for paste. In a lot of cases dealers will bulk it out with e.g. lactose or other wierd stuff.