A classifier and a method of separating material using such a classifier are disclosed. The classifier comprises a mixing chamber having a mixing fluidization floor and a concentration chamber having a concentration fluidization floor. The concentration fluidization floor and at least a portion of the concentration chamber is located below the mixing fluidization floor. The method of separating material using such a classifier comprises delivering material to be separated into a mixing chamber of the classifier, fluidizing the material in the mixing chamber; transferring some of the material to a concentration chamber of the classifier in fluid communication with the mixing chamber, fluidizing the material in the concentration chamber, forming a concentrating fluidized bed in the concentration chamber, separating the material with at least the concentrating fluidized bed and drawing heavier portions of the separated material from the concentration chamber.