The volcanic fi eld of Harrat Khaybar north of Al-Madinah, Saudi Arabia contains rare examples of white volcanoes comprised mainly of the felsic rock comendite. The obsidian that occurs in association with the white comendite was exploited and worked by Neolithic inhabitants of the area. The white volcanoes are surrounded by more recent black basaltic lava fi elds that follow the pre-existing topography and display both aa and pahoehoe fl ow structures. Although situated only 60 km from a busy

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... otorway, the volcanic area is remote and all necessary safety precautions must be taken in order to visit the volcanoes.