This sandstone district is cut into by deep gorges and canyons, that have sheer falls of several hundred feet in places. It comprises the mountains which yielded turquoise and copper, products that brought the neighbouring people into Sinai. Beads of turquoise were found in the pre-dynastic tombs of Egypt which probably came from Sinai, while there was an increasing demand for copper in the surrounding countries from the close of the Neolithic Age. If the name Milukhkha of the Babylonian records refers to Sinai, these people also came there several thousand years before our era. Turquoise appears in a ferruginous layer in the sandstone at the height of about 2650 ft. at Serabit, and at the height of about 1170 ft. at Maghara above sea-level. The copper ore occurs in the Wadi Nasb, and in the Wadi Khalig, somewhat extensively in the latter, together with iron and manganese. Enormous slag heaps lie at the head of the Wadi Nasb and near the outlet of the Wadi Baba, which bear evidence to former smelting activity. Again, in the Wadi Sened, a dyke rich in copper traverses syenite for a distance of nearly two miles. The district which was worked by the ancient Egyptians was comprised between the valley system of the Wadi Baba on the north, and that of the Wadi Sidreh on the south, both of which have their outlet in the direction of the coastal plain of El Markha. It was from this side that the ancient Egyptians approached Sinai. The chief height of the district is the Tartir ed Dhami (black cap), so called from the dark basalt that forms its summit, which rises to a height of 3531 ft. There is also the double-peaked Umm Riglên (mother of two feet) which rises to the south of the Wadi Umm Agraf and dominates the height of Serabit.