This ultrafine black powder is carbon black, a form of pure carbon (C) and the reason many rubber objects are black. Tires, shoe soles, and practically all rubber products where tensile and abrasion wear properties are important, are reinforced with carbon black. It is also a common pigment for black ink.
Carbon black is one of the oldest pigments and was used in cave paintings by prehistoric humans over 20,000 years ago.
