Gold is the most common and popular of the precious metals for most jewelry. Gold is weighed and valued by a system of karats, with 24 karats being pure gold, and is abbreviated after the value number as "K." Most people know that you can buy jewelry in 10K, 14K, 18K, and sometimes the full 24K (though this is rare). Gold is a very soft metal, so other metals are added into any jewelry of less than 24K, and typical alloys include zinc, silver, and copper.
When you're trying to identify how much gold you've got in a piece, you're looking for a 10K, 14K, or similar on the item. If you see certain letters after this value, such as GF, GEP, or P, it means that the item is gold plated and not solid.
When you're buying gold jewelry you should know how much gold is in the piece you're buying. This is even more important if you're selling scrap jewelry to a dealer or Jeweler. Otherwise you are almost certainly going to lose money in the transaction.
When selling gold jewelry you can weight it yourself on a scale that gives you grams, This way you will know the weights before you even go to sell. See below about pennyweights This is not good. Anyone advertising in penny weights are doing this to make it look and sound like your getting more money for your gold ,in fact your getting less. So if you hear this run the other way.
Also you will want to know what SPOT PRICE is right before you sell. ALL gold buyers go by this price to determine the pay-out to you. A great place to see this is www.kitco.com but remember this changes every 5min. or so Monday - Friday.