Abstract: A method of making low-density silica-alumina thermal insulation wherein sulfuric acid is used to leach clay fines from processed Athabasca oil sands. The treated fines are dried and roasted to produce a fine buff to white colored powder with particle sizes that range from forty microns to less than a micron. About 80% of these particles are less than twenty microns. The bulk density of this powder is about fifteen to thirty-five pounds to the cubic-foot (lb./ft.sup.3), compared to silica sand which has a bulk density of 150 lb./ft.sup.3, and alumina which is about 200 lb./ft.sup.3, depending on the grade and method of production.