Just like silver jewelry, there are many varieties of gold-looking jewelry in both the fine and fashion categories. Six types of golden jewelry include Gold, Gold Filled, Gold Plated, Rose Gold, Brass and Bronze.
Old gold jewelry is easy to identify because it does not tarnish. If your vintage or antique jewelry is clean and tarnished it is probably 24 K (karat) gold jewelry. New gold jewelry is not tarnished, but neither is new gold-plated, brass, or bronze jewelry. One way to test jewelry is to check for an identifying stamp. Typically, gold jewelry has a stamp in a hidden area with a number followed by the letter K (for karat). Sometimes stamped tags are near the clasp of a chain or of a bracelet. The higher the karat the greater amount of gold in the alloy. 24K is the purest form of gold jewelry. If the jewelry is not stamped you can try to determine if you have an alloy or another golden metal by softness.
Acid testing gauges the reaction of testing acid and your metal jewelry to determine its composition. You can buy a relatively inexpensive acid kit from amazon, test your items, and know exactly what you have in your jewelry box. These kits can also test for silver and other metals. If you are a collector, and especially if your starting out, this kit (or one like it) is a smart investment.
A less scientific method required the use of your teeth. Have you ever seen a cartoon character bite a coin? The character is testing a golden-colored coin for softness. Although you do not have to bite any of your jewelry. Instead, find an inconspicuous spot and press your thumbnail or similar semi-sharp object into the jewelry. This is not a perfect test, but the general rule of thumb is that higher karat pieces of gold jewelry are softer than lower karat items. The video below shows the effects of biting many different kind of metals, and gold vs. bronze at 3:06. He goes on to bite silver, and explain a little about gold alloys used in dental crowns.
Gold is a softer metal than bronze or silver so it easier to mar by any method, including biting. Gold filled jewelry is heavily plated Sterling Silver jewelry. The core of the item is sterling silver but the thickness and karat weight of the gold varies. Look for a stamp or tag. The stamp or tag will show a number followed by K (for karat) and GF (for Gold-Filled).
Gold plated jewelry is either copper, bronze, brass, stainless steel, steel, or sometimes aluminum jewelry with a thinner plating of gold on top. Steel is magnetic so you can use a magnet to see if the item contains steel. Also look for a tag to indicate the karat weight of the plating e.g. 24K GP, wherein GP stands for gold-plated.
Sometimes it is hard to tell what is gold and what is not. Sometimes jewelry is not marked. There are three gold coins mixed in the following six coins . Can you tell which ones they are? The first, third, and fifth coins are gold. They vary in shade and depth of color but all three are gold Dinar from the second century of the current era. Coin number two is a modern, gold-plated, copper-nickle coin from Australia. The fourth coin is a nickle-brass commemorative coin from Albania, and the sixth coin is a bronze token from Hampton Court Place.
The last golden tone on our list is Rose gold; a thin gold-plate over copper can come out as rose gold, but more typically, rose gold is a gold and copper alloy. The rose hue comes from the copper blended into the alloy. The coin below is a rose gold example from Australia.