Precious stones are as old as humanity. Precious or valuable stones are often found deep within the earth, but they only come to the surface after volcanic eruptions or earthquakes. Precious stones can also form deep within the seas and oceans, and they can sometimes be found above the earth's surface. We may sometimes think of mining as a modern industry, but it actually dates back to prehistoric times. This is indicated by archaeological evidence and mines dating back 4,100 years BC, where humans discovered the earth's treasures and the valuable minerals it contained. They worked to extract them and use them in the manufacture of their tools. Their use evolved with scientific progress day by day. The markets for most of these precious metals have formed the balance of the global economy, as their material value significantly impacts trade and financial exchange between countries. They have served as the basis for calculating the value of currencies internationally. Many of these precious metals are also used in the manufacture of coins and jewelry, and have been incorporated into the medical and therapeutic industries.