Kief, also known as keef, dust, chief, or even cannabis crystals, refers to an accumulation of loose cannabis trichomes collected from sifting flower through a sieve, grinder or mesh screen. The beige powdery substance that is left behind is kief and is quite a bit more potent than cannabis flower. Marijuana buds typically possess somewhere between 12% to 25% THC, whereas kief can be as high as 70% THC.