Gold is the world's most ancient and most coveted metal. Wherever it was mined or traded, it always represented wealth and power. The earliest known gold jewelry came from the Sumer civilization around 3000 BC, in an area that we now know as southern Iraq. Other ancient masterpieces were created across Europe, the Middle East, Asia, and South America. Gold's beautiful color and malleability inspired craftsmen to create ornaments and jewelry by developing techniques like chain-making, alloying, pounding, and lost-wax casting.
Pure gold is generally considered too soft to make into everyday jewelry. It bends, scratches, and wears away with friction. Even in ancient times, gold was frequently alloyed with other metals to keep its shining glow but with added strength, durability, and a range of colors. White gold's look is achieved by alloying gold with nickel, silver, or palladium. Red gold is created by alloying gold with copper. Most yellow gold contains varying amounts of nickel, copper, and zinc.
The purity of gold (or percentage of pure gold in an alloy) is measured in karats (kt). Karat should not to be confused with a "carat" (ct), the unit of weight for diamonds. Here's a quick chart to break down the conversion:
24 karat gold is currently very popular in Asia, where it has the Chinese name chuk kam. 10 karat gold is the lowest amount jewelers in the United States can call real gold. Most popular in the West is 14 or 18 karat gold, which is warmly lustrous and finely workable but strong enough to wear every day.
When gold is weighed, it is generally measured in grams (g) or ounces (oz). All real gold jewelry must have its karatage clearly stamped on it.
Gold is a mined metal, and sources have been found on literally every continent. But, until the California rush of 1848 (and the rushes that followed in Canada and Australia) gold was an extremely rare metal. Russian output accounted for 30-35 tons of world total gold of 75 tons by 1847. Now, the most productive gold mines are in South America, Africa, North America, and Australia.
Today, gold is used for everything from high tech semiconductors to gold crowns for teeth -- and of course, it is still one of the most desired jewelry metals everywhere. Right now, the world's mined gold equals more than 125,000 tons -- of that amount, 90% was mined after the California gold rush. While this increase is pretty amazing, what's even more incredible is that all the gold ever mined would form a cube only 19 meters per side.