Exploration of deposits of asbestos is more and more often conducted by drilling works. Almost all known deposits of chrysotile-asbestos of the USSR are explored by wells of core drilling.As the long-term practice of exploration of these deposits shows, at sampling of a core of the wells drilled on asbestos-bearing rocks, the definition of the content of fiber in ores is somewhat distorted. It is connected with relatively big abrasion of rocks on separate intervals of a core, with grinding of asbestos fiber at drilling. The nature of the process of abrasion of cores from asbestos-bearing rocks and the degree of distortion of determination of asbestos content during core sampling have not been studied sufficiently ...