As far as telling if street crack was based with NH3 or bicarb, I'd use a little distilled water to wet a platinum wire, or at poke it in if its really oily stuff, to make sure some adheres to the tip, and hold it in a flame. Sodium ions give a characteristic orange visual spectrum when vaporized and ionized. The platinum wire is so the metal won't contaminate the flame colour.
NH3 won't cause any colour change AFAIK, whilst sodium from bicarb would cause a bright orange tinge to the flame, using a blowtorch or something similar. Various elements give characteristic flame discharges or when vaporized and ionized in a discharge tube. For example copper and barium give two different greens, copper being darker, barium being lighter, more vibrant, like growing plant leaves, whilst lithium for example gives a brilliant scarlet tinged with purple, potassium burns purple and caesium blue.
