Abstract: A nozzle for fluidizing particulate material, such as mine tailings, comprising a body having a rear inlet end and a cylindrical surface adjacent a front end, the body having a passageway leading from the rear end to an outlet orifice located in the cylindrical surface, with the passageway including an outlet portion diverging at an acute angle from a central axis of the cylindrical surface. The nozzle also has a resilient sleeve surrounding the cylindrical surface and which is capable of sealing the orifice when pressure in the passageway is low relative to pressure in the slurry outside the nozzle. The sleeve is expandable to allow fluid under pressure to exit the nozzle in a generally forward direction when fluid such as water is supplied to the rear end of the nozzle. The invention also includes a self-closing mounting fixture located in the wall of a vessel such as a silo, which prevents escape of slurry from the silo when the nozzle is removed from the fixture for servicing or exchange.