Ultramafic ores are a potential major resource of nickel. For the Thompson area deposits of northern Manitoba, Canada, a processing challenge is the serpentine polymorph chrysotile, the dominant gangue mineral. Due to its fibrous nature chrysotile causes physical entanglement and increased pulp viscosity which reduces selectivity in flotation. The proposed approach involves disintegration of the fibers by a combination of chemical (H2SO4) and mechanical (grinding) treatment adapting technology explored for CO2 sequestration. The use of H2SO4 also led to collectorless flotation traced to elemental sulphur formation, and release of magnesium increased solution ionic strength sufficient to eliminate the need for frother. Significant improvement in Ni grade-recovery with higher rejection of MgO-bearing gangue was achieved compared to untreated ore. Structural changes in the fibers were followed using spectroscopic techniques. A mechanism of fiber disintegration is suggested. (C) 2011 Elsevier B.V. All rights reserved.