Crack cocaine is the freebase form of cocaine that can be smoked. It may also be termed rock, hard, iron, cavvy, base, or just crack.
In purer forms, crack rocks appear as off-white nuggets with jagged edges, with a slightly higher density than candle wax.
Purer forms of crack resemble a hard brittle plastic, in crystalline form (snaps when broken). A crack rock acts as a local anesthetic (see: Cocaine), numbing the tongue or mouth only where directly placed.
When smoked, crack can leave the tongue numb where the smoke enters the mouth. Purer forms of crack will sink in water or melt at the edges when near a flame (crack vaporizes at 90 °C, 194 °F).
Crack cocaine as sold on the streets may be adulterated or “buffed” to increase bulk. According to Cpl. Kent Dahl, with Red Deer RCMP Federal Drugs, Canada, white substances mimicking the appearance of cocaine are added to increase bulk.
Use of toxic adulterants such as levamisole has been documented.