Gold is Rated by Its Purity
You may have often heard of the terms 10 karat (10k) or 24 karat (24k) Gold. The higher the karat, the purer the gold. 24 karat is considered pure gold or 99.9% pure. Pure gold, like pure silver is too soft to be used in making most jewelry, gold is often mixed with other metals to give the item strength. The karat value reflects the percent of gold in the the jewelry. 24K gold is considered pure, but 10K is ten parts gold and the rest is a mixture of other metals. Most fine jewelry uses 18K gold or higher. Most yellow gold contains copper & silver.
Most white gold contains nickel, zinc and copper. Gold will never turn a finger or neck dark – it is the alloy mixed with the gold that does the turning. Sometimes it is only temporary due to the person’s internal chemistry from a stressful situation, food or medicine that was recently ingested.
Most of the gold that is fabricated today goes into the manufacture of jewelry, but gold is also an essential industrial metal that performs critical functions in computers, communications equipment, spacecraft, jet aircraft engines, and a host of other products.