Because shell has small and exquisite appearance, bright color, solid texture, and the feature of easy to carry and count, shell is used as a kind of primitive money circulated at the end of the Neolithic Age. Shell money is a kind of commodity money lasting the longest time. The unit of shell money is 芒鈧減eng芒鈧劉 (忙艙鈥?in Chinese, means friend), which originally means two clusters of shells. Generally speaking, one peng is made up by two clusters of 10 shells. At the end of the Shang Dynasty (1675 BC芒鈧€?029 BC), due to the lack of shells in Northeast China, there were other forms of shell money which can be made of pottery, stone, bone, jade, copper and gold. However, the most common one is made from natural shells.
The invention of shell money which made of copper at the end of the Shang Dynasty (1675 BC芒鈧€?029 AD) marks the beginning of the use of metal coins in China.