Retractable pin mixing sample forming device

A device for processing a material comprising

• a mixing chamber having a valve for removal of the material from the mixing chamber and a piston which fits within the mixing chamber in a manner such that the piston can be moved to remove substantially all material from the mixing chamber via the valve;
• at least four retractable mixing elements wherein such elements are movable in and out of the mixing chamber through a port wherein the elements and ports are configured such that during mixing and when the elements are withdrawn from the mixing chamber substantially no material is removed from the mixing chamber via the port, and wherein the mixing elements rotates, and wherein the mixing chamber, piston and retractable mixing elements are cylindrical and the retractable mixing elements are arranged in a rectangular, square or diamond-shaped array such that there are two diagonally opposite pairs of mixing elements and the two pairs of diagonally opposite mixing elements rotate in opposite directions.