Crack cocaine. Rocks of crack cocaine. Crack is the street name for an almost pure form of the illegal drug cocaine. Conventional cocaine powder consists mostly of cocaine hydrochloride, which is destroyed by heating and therefore impossible to smoke. Crack is prepared by mixing ammonia with a solution of cocaine hydrochloride, which causes the alkaloidal pure cocaine to be precipitated (free base). This is then compacted into rocks and smoked in a pipe. The drug is absorbed through the lungs much more quickly than snorted cocaine, producing an intense but short- lived rush.