Although early settlers on the Indus plains participated in well-established trade networks across the Iranian plateau, their descendants started to trade directly by sea via the Persian Gulf with the towns of Sumer. Sumerian texts speak of traders from Meluhha, their name for the Indus civilization.
Indus material has been found not only in Mesopotamia but also in Dilmun (Bahrein) and Magan (Makran and Oman). Nothing remains of Mesopotamia's exports to the Indus, however, since these were mainly perishable goods like fine woollen textiles.
Lothal, situated near the coast in Indus times, was probably important in this trade. Here finds include a Dilmun seal, a large warehouse with many sealings from consignments of merchandise and a large basin thought by some scholars to have been a dock.
Pictures of ships on seals show that the Indus folk had sea- and river-worthy craft. These transported not only Indus products like carnelian beads and Himalayan timber but also one of antiquity's most precious commodities, lapis lazuli from Badakshan in Central Asia.
Near here at Shortugai, the Indus people established a trading colony, essentially no different from other Indus towns, through which to monopolize the supply of lapis to the west. Interestingly, little lapis was found on Indus sites - presumably it was more valued by the Indus folk for its buying power than for its own sake.
