How to Tell if Gold Is Real
To tell if gold is real, try dropping it into a glass of water. If it floats, it's probably not real gold, since gold is very dense. You can also try holding a strong magnet, like the kind you can find at hardware stores, up to the metal to see if it sticks to it. If it sticks, it probably isn't real gold, since gold isn't magnetic. Alternatively, try rubbing the metal on a piece of unglazed ceramic to see if it leaves a gold streak, which could be a sign that the gold is authentic.
Look for an official number marking on the gold. The marking, or hallmark, tells you what percentage of gold an item consists of. The hallmark is often printed on jewelry clasps or the inner bands of rings. It is usually visible on the surface of coins and bullion. The stamp is a number from 1 to 999 or 0K to 24K depending on what kind of grading system was used. Use a magnifying glass to help you identify the hallmark. It can be tough to make out by eye, especially on smaller pieces of gold such as rings. Older pieces of jewelry may not have visible hallmarks. Sometimes the hallmark wears off over time, while in other cases the jewelry never got a stamp. Hallmarking became common in the 1950s in some areas, but in India for instance, it only became mandatory in the year 2000. Use the number marking to determine how much gold is in your piece. Most coins and jewelry are not pure gold, so they have other metals mixed in. There are 2 different scales used to indicate this through the hallmark. The number rating system used in Europe runs from 1 to 999 with 999 meaning pure gold. The U.S. uses a scale from 0 to 24K, where 24K is pure gold. The number rating system is easier to read than the karat rating system. For example, a rating of 375 means your item consists of 37.5% gold. What number means gold depends on the country you are in. In the U.S., for example, anything 9K and under is not considered to be gold, even though a 9K bracelet consists of 37.5% gold. Counterfeit pieces may have markings making them look authentic, so don't go solely on the hallmark unless you're certain you are holding gold. Check for a letter marking indicating that the gold isn’t pure. Some of the common letters you may see are GP, GF, and GEP. These letters indicate that your gold piece is plated, which means the maker put a thin layer of gold over another metal, such as copper or silver. Your item has some gold in it, but it isn't considered to be real gold. GP stands for gold plated, GF means gold filled, and GEP means gold electroplate. The markings vary a little depending on where the gold is from. For instance, gold from India contains a small triangle symbol indicating the government council responsible for the rating system. It then has a number rating and a letter code, such as K, for the jeweler. Find any noticeable discolorations where the gold has worn away. Gold is pretty soft for a metal, so plated gold often rubs away over time. The best places to check are around the edges of jewelry and coins. These spots often rub up against your skin and clothing throughout the day. If you see a different metal underneath the gold, you know your item is plated and not considered real gold. For example, a silver coloring might indicate silver or titanium. A red coloring could mean copper or brass. Note any discolorations on your skin from wearing or holding the gold. Pure gold doesn't react with sweat or oil from your skin, so if you see black or green marks, they are from other metals. Silver leaves behind black marks and copper leaves behind green marks. If you see a lot of these marks on your skin, your gold may be less pure than you expect. Keep in mind that most gold items are blends of gold and other metals. Even something like a 14K piece of jewelry, 58.3% gold, can leave these marks. Use other tests as well to ensure your gold is authentic. Drop gold into a jug of water to see if it sinks. Get container big enough to hold both the water and the gold you wish to test. The water temperature you use doesn't really matter, so lukewarm water is fine. Real gold is a dense metal, so it falls directly to the bottom of the jug. Imitation gold is much lighter and floats. Real gold also doesn't rust or tarnish when wet, so if you see a discoloration, you probably have plated gold. Hold a strong magnet up to see if the gold sticks to it. For this test, you need a strong magnet capable of pulling even metal blends. Move the magnet over the gold and observe how it reacts. Gold isn't magnetic, so don't be fooled by anything that sticks. If the magnet pulls the gold toward it, your item is either impure or a fake. Regular kitchen magnets won't do. Buy a powerful neodymium magnet from a home improvement store. The magnet test isn't foolproof, since counterfeit gold can be made with non-magnetic metal like stainless steel. Also, some genuine gold items are made with magnetic metals such as iron. Rub the gold on a unglazed ceramic to see if it leaves a streak. Make sure you're using an unglazed piece of ceramic since anything with a glaze could affect the test results. Drag your item across the plate until you see some fragments coming off the gold. If you see a black streak, that means your gold is not real. A gold streak usually indicates authentic gold. Try getting an unglazed ceramic tile or a plate online or from your local home improvement store. This test scratches the gold a little bit but doesn't typically leave much noticeable damage. It is much safer than other tests involving scratches or acid. Another way to do this is by spreading some cosmetic foundation on your skin and dragging the gold across it after it dries. Fake gold usually reacts with the foundation, leaving a green or black streak in it. Weigh your piece of gold on a scale. If you have a decent kitchen scale, place the gold on it. Otherwise, jewelers and appraisers often can do it for you for free. Call around to different jewelry or appraisal stores to see which ones offer this service. Make sure you get the weight in grams rather than ounces. You need the weight in grams to use in a calculation later. If the weight is in ounces, you won't get an accurate result. Fill a graduated cylinder halfway full with water. Choose a cylinder that is big enough to hold the gold. It needs to have measurement markings in milliliters (mL) or cubic centimeters (cc). If you don't have a regular graduated cylinder, you could try using a kitchen measuring cup. Vials with frequent millimeter markings on the side are useful for getting a more accurate measurement during the test. The amount of water you use doesn't matter that much as long as you leave plenty of space for the gold. If you fill the vial to the top, dropping the gold into it causes the water to spill. Read the starting water level in the cylinder. Look at the markings on the cylinder, then record the water level. This measurement is very important for the test, so write it down. Make sure you have the vial on a flat, level surface in order to get as accurate a reading as possible. Keep in mind that it doesn't matter if your vial is marked in milliliters or cubic centimeters. They are the same measurement, so either unit can be used in the test. Drop the gold into the vial and record the new water level. Gently lower the gold into the cylinder to avoid losing any of the water. Let go of it right above the water to prevent splashing or getting your fingers wet. Then, read the markings again to get the second measurement. Write the second measurement down on a piece of paper. Note that this is the second measurement, not the initial one. Subtract the measurements to find the difference in the water level. Perform a simple calculation to figure out how much water the gold displaced. Subtract the initial measurement, the smaller number, from the final measurement. This gives you an answer in milliliters or cubic centimeters, depending on what measurement your vial lists. For example, if you started with 17 mL (0.57  fl oz) of water that rose to 18 mL (0.61  fl oz), that leaves a 1 mL (0.034  fl oz) difference. Divide the gold’s weight by the difference in the water level. The density of the gold equals its mass divided by its volume. After calculating the density, compare the result to the standard density of gold, which is 19.3 g/mL. If your number is way off, chances are you have a fake. Keep in mind, though, that some combinations of metals in fake gold can have a density similar to real gold. For instance, you have a gold item that weighs 38 g (1.3 oz) and displaces 2 mL (0.068  fl oz) of water. Divide 38 by 2 to get 19 g/mL, which is very close to the density of gold. The standard density differs a little depending on the type of gold you have. For 14k yellow gold, it's about 12.9 to 13.6 g/mL. For 14K white gold, it's around 14 g/mL. A piece of 18K yellow gold has an average density from 15.2 to 15.9 g/mL. A piece of 18K white gold has a density from 14.7 to 16.9 g/mL. Any 22K piece of gold has a density around 17.7 to 17.8 g/mL. Purchase gold-testing kit to get the acid you need for the test. Testing kits include various bottles of nitric acid for different types of gold. Some tests also include a flat rock called a touchstone you can use to scratch off some of the gold on your item. You may also see needles with samples of yellow and white gold to use as a comparison to your item. Testing kits are available online. Also, check with local jewelry stores. Most jewelers use this test for its accuracy. Create a small scratch on the gold using a sharp tool. Choose an inconspicuous location on the jewelry to make the scratch, such as underneath a clasp or an inner band. Then, use a sharp tool such as a jewelry engraver to dig into the gold. Scratch until you get underneath the top layer of gold. Expose a fresh layer of gold or any other metal underneath it. Nitric acid tests require you to scratch your piece of gold. If the gold has personal value to you or you plan on keeping it, take it to a professional jeweler instead of doing the test yourself. Add a drop of nitric acid to the scratch. Put on latex gloves and work in a well-ventilated room to avoid any issues with the dangerous acid. When you're ready, look for the bottle of acid labeled for 18K gold. After setting the gold in a stainless steel container, place a drop of the acid directly on the scratch you made, then watch for it to turn a shade of green. If it turns green, you know right away your gold is fake. Regular gold does not react to the acid, so your item might be gold plated or a low-purity blend of metals. A milk-colored reaction usually indicates gold-plated sterling silver. If the acid turns gold, you have gold-plated brass. Scratch the gold on a touchstone to test its purity. If you think you might have real gold, rub it along the touchstone to create a streak of gold flakes. Add a drop of 12K, 14K, 18K, and 22K nitric acid to different parts of the streak. Check back after 20 to 40 seconds. Find the spot where the acid doesn't dissolve the gold to figure out what karat rating your item is. The acids all increase in strength, so the acid used for 22K is stronger than the 12K one. If the 18K acid dissolves the gold but the 14K one doesn't, you know your item is probably around 14K. 
Look for an official number marking on the gold. Use the number marking to determine how much gold is in your piece. Check for a letter marking indicating that the gold isn’t pure. Find any noticeable discolorations where the gold has worn away. Note any discolorations on your skin from wearing or holding the gold. Drop gold into a jug of water to see if it sinks. Hold a strong magnet up to see if the gold sticks to it. Rub the gold on a unglazed ceramic to see if it leaves a streak. Weigh your piece of gold on a scale. Fill a graduated cylinder halfway full with water. Read the starting water level in the cylinder. Drop the gold into the vial and record the new water level. Subtract the measurements to find the difference in the water level. Divide the gold’s weight by the difference in the water level. Purchase gold-testing kit to get the acid you need for the test. Create a small scratch on the gold using a sharp tool. Add a drop of nitric acid to the scratch. Scratch the gold on a touchstone to test its purity. 