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Impact Abrasion of Harder by Softer Materials

Fluorite, halite, periclase, and sylvite have been abraded in a wind tunnel by windblown dust from the "normal" air of the intake room plus or minus introduced silt-sized particles of calcite, barite, or snow. The results indicate that the effective kinetic energy of a projectile and the bond strength of the target-rather than hardness differences, per se-may be fundamental controls of windblast abrasion. It is concluded that, contrary to general belief, some windblast erosion features have probably been produced in response to impact by relatively soft and/or small missiles, such as snow and dust, moving at fairly low wind velocities.