If you are wondering if the gold you bought or found at home is real, the surest way to know is to take it to a jeweler and have it examined. However, if you want to check for yourself, here is a list of tests you can run to determine it.
Steps
Method 1 of 6: Visual Exam
The first thing to do to check if your gold is real is to take a look at it. Look for particular signs or indications that denote purity (or not).
Step 1. Examine the piece for official writing or markings
If you find a hallmark (a mark embossed in the metal), it should indicate the purity of the gold, expressed in thousandths (1-999 or 0, 1-0, 999) or in carats (10k, 14k, 18k, 22k or 24k). Generally gold objects have no less than 9 carats (in America any artefact with less than 10k is considered fake gold) and always bear the punch indicating the carat weight. Using a magnifying glass will make it easier for you to locate the punch and, if it is not present, it is possible that the object is fake.
- It is possible, especially on older items, that the punch is illegible or has disappeared due to wear.
- Counterfeit items often have a stamp that looks authentic. However, further tests may need to be conducted.
Step 2. Check if there is a noticeable color difference
It is important to check the color of the surface in the areas most exposed to friction (usually around the edges) as it is easy to see if the object is only coated with gold or is solid gold.
If the gold seems to come off and you can see a different colored metal surface, the object is probably just covered with gold
Method 2 of 6: Bite Test
Who hasn't seen in the movies a gold digger, a goldsmith or a bank clerk biting into a gold coin to check if it's true? We also see Olympians biting their "gold" medals upon delivery (that this has any use, is a separate case).
Step 1. Bring your gold to your mouth and bite it
Step 2. Check if there are any marks left on your gold
In theory, real gold should have notches left by your teeth - the deeper the notches, the purer the gold.
This is not a recommended method, mainly because: it can damage your teeth; damages gold; there are metals, such as lead, which are even softer than gold and can make what could be, for example, just lead covered in gold, look like gold
Method 3 of 6: Proof of the Magnet
This is a very simple test, but it is not an absolute test or a foolproof method to determine if your gold is real or not. A weak magnet, such as those you put on the fridge, is not enough, but you can use stronger magnets, such as those found in home improvement stores or in common items (in women's bag closures, in children's toys or even old hard drives), to conduct this test.
Step 1. Hold a magnet near the object
Gold is a diamagnetic metal (i.e. it does not react to magnetic fields), therefore, if the object is attracted to the magnet it is false. However, the fact that the object is not attracted to the magnet does not mean that the material is gold, as other diamagnetic metals are also used to counterfeit gold objects.
Method 4 of 6: Density Test
There are very few metals denser than gold (and they are all very rare metals, some not even existing in nature). The density of pure gold at 24k is around 19.32 g / cm3, a very high value compared to that of the most common metals. Measuring the density of your items can help you determine if your gold is real. Generally, the higher the density, the purer the gold. Remember that this test only works best if the item is made entirely of gold - the presence of gems or other decorations will invalidate the result. Read the Warnings section below to learn more about the density test.
Step 1. Weigh your gold
You can ask a jeweler or goldsmith to do it for you (they usually do it for free) if you don't have a suitable scale. You will need the weight in grams.
Step 2. Fill a tube with water
- If possible, use a test tube or container with a graduated scale, as this will make it much easier to measure for this test.
- The quantity of water you use is not important, as long as you do not fill the tube to the brim: we must in fact immerse the gold in the water and the liquid level must necessarily rise.
- It is also important to remember to mark the water level before and after the dive.
Step 3. Immerse your gold in the water from the test tube
Mark the new water level and calculate the difference between these two numbers, expressing it in millimeters.
Step 4. Use this formula to calculate the density:
ρ (density) = m (mass) / V (volume). A result close to 19 g / cm3 indicates that the object is made of real gold, or a metal with a density similar to that of gold. Here is a calculation example:
- Your gold object weighs 38 grams and raises the water level by 2 milliliters on the graduated scale (i.e. it has a volume of about 2 ml). Using the formula m / V = 38 g / 2 ml, the result would be 19 g / ml (1 ml = 1 cm3), which is a value that is very close to the density of pure gold.
- Keep in mind that the purity of gold affects the density, so you will get different values depending on the carat:
- 14k yellow - 12.9 to 13.6 g / ml
- 14k white - from 12.6 to 14.6 g / ml
- 18k yellow - from 15.2 to 15.9 g / ml
- 18k white - from 14.7 to 16.9 g / ml
- 22k - from 17.7 to 17.8 g / ml
Method 5 of 6: Test the Ceramic Plate
This is a super easy way to tell if your gold is real or foolish gold. It is best not to use this test with crafted or fine items, as they can get damaged.
Step 1. Look for an unglazed ceramic plate
If you don't have one (or don't want to risk ruining it), you can buy any unglazed ceramic piece (e.g. a tile) at a home improvement store.
Step 2. Rub the gold object on the ceramic surface
If it leaves a black stripe, it means your gold is fake, otherwise, if you see a gold stripe, your item is made of real gold.
Method 6 of 6: Nitric Acid Test
This is a great method of determining if gold is true, however, due to the difficult availability of the acid and the safety risks involved in conducting this test at home, it is best to leave this test to professional jewelers and goldsmiths..
Step 1. Place your gold item in a small stainless steel container
Step 2. Drop a drop of nitric acid on the gold and observe the reaction to the acid (if any)
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If the material turns green, then the object is made of a base metal or is just covered with gold.
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If the material turns milky, then the item is made of sterling silver and covered with gold.
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If no reaction is observed, then your object is probably made of solid gold.
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Advice
- When we say "24 karat" (or 24k), we mean that 24 out of 24 parts of the material are pure gold, free from traces of other metals. In this case, gold is considered 99.9% pure. In 22k gold there are 22 parts of gold and 2 parts of some other metal (91.3% pure gold). In 18k gold there are 18 parts of gold and 6 parts of some other metal (75% pure gold), this composition is often used in jewelry since alloys with particular metals (silver, copper, palladium, nickel) take on different colors. As the carat goes down, the purity of gold decreases (each carat is equivalent to approximately 4.1625% of the total).
- In gold with less than 24k there are alloys that give the material certain characteristics of hardness and color. It can be said that 24k is the softest, while 10k is the hardest, since 10k has a gold percentage of 41.6% and the rest is made up of other metals, which are harder than gold.. The color of other metals and alloys embellishes and sharpens the beauty of jewels, such as those found in white gold, yellow gold, rose gold etc.
- 24k gold is pure gold, but it is generally too soft to be used in jewelry or coins and, for this reason, alloys are made with other metals to increase hardness. This, however, causes differences in density depending on the gold percentage of the material.
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The punches on gold jewelry produced in Europe are different from American ones and indicate the purity of the gold of the material. The writing usually consists of three digits to be interpreted as follows:
- Hallmark 417 (10k): 41.7% pure gold
- Hallmark 585 (14k): 58.5% pure gold
- Hallmark 750 (18k): 75% pure gold
- Hallmark 917 (22k): 91.7% pure gold
- Hallmark 999 (24k): 99.9% pure gold
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In Portugal, 80% pure gold (about 19.2k) is almost always used and can be found in three colors:
- Yellow - composed of 80% gold, 13% silver and 7% copper.
- Red - composed of 80% gold, 3% silver and 17% copper.
- Gray or white - composed of 80% gold alloyed with palladium and other metals (especially nickel).
Warnings
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Notes on the density test:
- The density test is not the most accurate method of determining whether gold is true or false, unless you know exactly the composition of your material and its relative density characteristics.
- Since very accurate calculations and measurements are required to obtain reliable results from the density test, it is good to know that this test is not very reliable if you do not have a test tube or graduated cylinder with some sensitivity in millimeters.
- Many jewelry and objects, which appear to be solid gold, are actually hollow. If there is air trapped inside the object, then the result of the density test will surely be wrong, as the air has a much lower density and yet still contributes to the total volume of the measured object in water. The density test is valid only for massive objects, or for hollow objects from which, however, the air can escape completely to make room for water (for example, those that have the shape of a vase). The presence of even a single air bubble inside the object during the test can invalidate the result.
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Nitric Acid Test Warnings:
Nitric acid is highly corrosive. If you decide to use it yourself for testing, remember to wear protective gloves and goggles and do not breathe its fumes. Pure gold objects are not affected by acid, but everything else (containers, tools, etc.) can easily be damaged in the process if not suitable for such use
- Using these tests, you may still not be able to distinguish a solid gold object from one composed of a tungsten backing that is only coated with gold.
