Why do you say that the gold currency was introduced by Lydia?

Lydia was an ancient kingdom in  Western Turkey. The country is fertile, but its  greatest asset is the small river Pactolus, which carries gold deposits. These gold deposits were believed to have originated when King Midas  washed himself in the river to cleanse himself of his ' golden touch '.
Around 643 to 630 BC, the Lydians started to produce the first coins. There were quite crude, and were made of electrum, a pale yellow mixture of gold and silver. By about 560 BC, the Lydians had learned how to separate gold from the silver, so that King Croesus was able to issue the worlds first gold coins. Shortly afterwards 546 BC was captured by the Persians, who came to adopt gold as the main metal for their coins. Soon gold coins were being used in several ancient countries, but the honour of introducing gold currency goes to Lydia.