Changes

===Later Developments===

While gold gained increased importance in places, particularly as international trade developed more formally in the 3rd and 2nd millennium BCE across the Mediterranean and Central Asia, from there the worth of gold did stall for a period. The next period of expansion likely occurred when coinage was developed. Sometime by the early 6th century BCE, silver and gold were now used to create coins. As coins were intended to symbolize value, it was important now that gold had to be pure. In fact, electrum, which combined silver and gold, was outlawed in Lydia, which has been considered the first state to use coinage. The use of coinage was initially in international trade. As empires developed across the Mediterranean in the mid to late 1st millennium BCE, that now connected the Mediterranean basin with Central Asia and India, coinage became more important for trade. The rise of the Achaemenid and particularly Greek-based empires in Bactria and Seleucia helped spread coinage to many regions. Gold now became the key material that was used for the most valued exchanges across much of the Old World. Expanding Greek colonies in Europe, increased trade across Central Asia, which became the Silk Road, and seaborne trade via India and the Arabian Sea became some of the most important trade routes in the Roman and late Classical period.<ref>For more on the role of gold coinage in international trade, see: Harris, Edward Monroe, David Martin Lewis, and Mark Woolmer, eds. 2015. <i>The Ancient Greek Economy: Markets, Households and City-States.</i> New York: Cambridge University Press.</ref>