Rare anthropogenic and natural particles suspended in deep ocean waters

Four hundred membrane filters from the Atlantic and Pacific deep waters have been scanned for coloured and opaque particles by a method integrating the light and the scanning electron microscopes, the electron microprobe and the micro-X-ray diffraction camera. About 40 different types of particles have been found. A tentative classification of the particles and of their morphological and chemical varieties is presented, according to their anthropogenic or natural origins. From this point of view, the particles fall into five groups: (1) particle species exclusively produced by man's activities (like brass, cobalt aluminate); (2) particles exclusively produced by natural processes (like amphibole, ilmenite); (3) particles rarely produced by natural processes, but massively so by man (like metallic copper, chromium oxide); (4) a large group of particles massively produced by nature and by man (like magnetite spherules, malachite); (5) a very small group of particles whose origin could not be attributed at present. Very few entirely new compounds from the point of view of continental mineralogy have been encountered.