Sediment cores from the Romanche Fracture Zone (RFZ) in the equatorial Atlantic have been described visually and microscopically as well as analyzed by X-ray diffraction techniques in order to study the main controls on their lithology, colour and mineralogy. The sediments display graditional changes in colour, mineralogy and lithology. Water depth and biogenic dissolution appear to play an important role in controlling the lithology and mineralogy of the sediments. Distance from continental and volcanic sources of sediment appear to play secondary roles. Changes of colour downcore largely reflect variation in the Mn and Fe oxides content of the sediments.