I thought it would be neat to have some informational threads in here since I'm sure many of you have things to add. So let's start with the basics.... The definition of "Solid Gold" per US standards, an item that is at least 10K gold all the way through. Even though it contains other metals-18K, 14K, or anything down to 10K (41.7% gold), it is still called solid gold. Gold does not tarnish, rust or stain your finger. Note: In Canada and Mexico, the minimum legal standard for gold is 9k and 8k. Karatage (Gold): Karat refers to gold purity or the parts of gold used in a piece out of 24 parts (not to be confused with carat which refers to the weight of a gemstone). 24k gold, or 24 parts is 100% gold. 14k gold or 14 parts, is composed of 58.3% gold, and 41.7% other metals. 18k gold is 75% gold and mixed with other metals to give it strength for daily wear. 22k is 91.7% gold. You will see the marking 10k, 12k, 14k, 18k to denote the karat of gold, however, many older jewelry pieces from the 19th century are not marked. European jewelry is often marked 585 for 14k gold and 750 for 18k gold. What about colored gold? This is my personal favorite topic. By mixing and changing alloys, you change the color of the gold. Using Nickel or Palladium will turn the gold, white. Using copper will turn it reddish and give you pink/rose gold. The type and percentage of metal alloys in gold are what determine its color. Here is a Gold Terminology article I wrote: http://www.futurefashionista.com/howtogold.html Feel free to add any information you would like.