The archaeologist Leonard Woolley found these beads and pendants in the burial shaft and on the floor of one of the first Royal Graves at Ur to be excavated. The objects on the floor of the tomb may have belonged to human attendants, as discovered in similar tombs, while those found in the shaft may have been left as offerings, when the tomb was being filled with soil after the burial. Sumerian craftsmen were highly skilled in stone and metalwork. Beads found in graves of this period were generally made using only four materials: gold, lapiz lazuli, carnelian and silver. The skill shown in gold-working is particularly impressive. A fine wire of gold is made into a spiral to form the double pendant in the centre string, and tightly coiled and soldered wire is also used to form the outer gold beads in the top string. Four cones of coiled gold wire soldered on to a gold disc form the central pendant in the top string, along with cones strung as beads on either side. Necklaces and diadems are known from as early as 7000 BC in northern Mesopotamia. Local stone was used. Later, more exotic stones and shell were brought into the region by trade or conquest. Among the most prestigious and valuable of stones was blue lapis lazuli from Afghanistan. In ancient documents, the stone was associated with gods and heroes, and 'lapis-like' was a standard way of describing unusual wealth.