Easily carved chloritite has been used in the Oman peninsula to produce vessels since the mid-third millenium BC, and has been widely exported over the whole Middle East. A detailed geological, petrographical and mineralogical study has shown that chloritite is available within the Semail ophiolite associated to hydrothermally altered pyroxene peridotite and amphibole gabbros of the mantle-crust transition zone. The small volumetric importance of single chloritite outcrops and the great variability of composition suggests exploitation of several extraction sites along the 500 km long Semail ophiolite. There is an abridged English version. -English summary