One of the oldest civilisations known to man, the Sumerians of Mesopotamia, who lived in what is modern-day Iran and Iraq, first used gold as sacred, ornamental, and decorative instruments in the fifth millennium B.C. Around the same period, the early Egyptians the richest gold-producing civilisation of the ancient world began the art of gold refining. Like the Sumerians, the Egyptians used gold primarily for personal adornment, rather than for monetary purposes, although the kings of the fourth to sixth dynasties (c. 2700 - 2270 B.C.) did issue some gold coins. The first large-scale, private issuance of pure gold coins was under King Croesus (560-546 B.C.), the ruler of ancient Lydia, modern-day western Turkey. Stamped with his royal emblem of the facing heads of a lion and a bull, these first known coins eventually became the standard of exchange for worldwide trade and commerce.:clap: