They consist chiefly of sands and clays of aeolian and freshwater origin.
Long; they collect from 10 to 15% of the whole gold; a further quantity is recovered by leading the sands through a gutter about 16 in.
By a branch railway, is in favour as a watering-place, having fine sands beneath the cliffs.
Its northern fringe is no doubt frequented by the Bedouin tribes of southern Nejd after the rains, when its sands, like those of the northern desert, produce herbage; but towards the east, according to Burckhardt's information, it is quite without vegetation even in the winter and spring.
The Nafud sands, too, are tufted in many places with bushes or small trees, and after the winter rains they produce excellent pasture.