A method of analysis of aggregate flow inside a flotation cell using a unique device called the Luba Tube is presented. The Luba Tube enables sampling and recording of the aggregate flow inside a flotation cell, beneath the froth layer. Size, shape, rise velocity and number of aggregates, floating in a separation vessel in an oil sand low-energy extraction process, were determined. For a separation vessel of 5.2 m in diameter used in a field pilot of 100 t/h, it was found that bitumen was transported to the froth layer in the form of irregular particles attached to air bubbles. A wide range of bitumen-air aggregate size from 0.13 mm to 2.84 mm was observed. Rise velocities of bitumen-air aggregates were determined from measurements of their position on subsequent frames of video recordings. Substantial differences in the number of aggregates floating to the froth layer were found at different radial locations in the separation vessel indicating non-uniformity across the vessel. The dependence of the number of aggregates on radial location in the separation vessel, found using the Luba Tube measurements, was in agreement with independent macroscopic measurements.