Look for fading around the edges of the piece

To check if a piece is pure gold, turn on a bright light or lamp and hold the piece close to it. Rotate the item in your hand, paying particular attention to the edges. If the gold appears faded or worn away at the edges, it’s likely due to wear on the plating. This indicates that the piece is gold-plated, not solid gold. Pure gold should maintain its colour and shine across the entire piece without noticeable fading.

Look for spotting on the piece’s surface

Hold the piece under a bright light and carefully examine it for any tiny white or red spots. These spots can be difficult to spot, so using a magnifying glass may help. If you notice such spots, it could indicate that the gold plating is wearing away, exposing the metal underneath. This suggests the item is gold-plated rather than solid gold. Genuine gold won’t show these signs of wear, as it is uniform throughout the piece.

Place a magnet against the potential gold item

Hold the piece under a bright light and carefully examine it for any tiny white or red spots. These spots can be difficult to spot, so using a magnifying glass may help. If you notice such spots, it could indicate that the gold plating is wearing away, exposing the metal underneath. This suggests the item is gold-plated rather than solid gold. Genuine gold won’t show these signs of wear, as it is uniform throughout the piece.

Apply some vinegar to the surface and look for a colour change

Fill a dropper with white vinegar and place a few drops onto the metal object, holding it firmly. If the metal changes color, it indicates that the piece is not pure gold, as vinegar can cause reactions with base metals. If the color remains the same, the item is likely pure gold, as gold doesn’t react to vinegar.

Rub your gold against a jeweller’s stone

Position a black jeweller’s stone on a table and hold your gold piece firmly. Rub it across the stone with enough pressure to leave a mark. If the mark is solid and gold in colour, the piece is likely pure gold. If there’s no mark or only a faint one, the piece is probably gold-plated or not gold at all. Be cautious with this method, as it can damage the jewellery. Use the proper jeweller’s stone, available from jewellery supply stores or local jewellers.

Use an electronic gold tester

A gold tester is a hand-held device with a probe, available online or at jewelry supply stores. To use it, apply a conductive “tester” gel to the metal item, which is also available from these stores. After applying the gel, rub the probe against the metal. The tester measures how the metal reacts to electricity. Pure gold will show higher readings than gold-plated items because gold is a highly conductive metal. Be sure to follow the instructions that come with your tester to interpret the results accurately, as different metals will respond differently to the device.

Insert your gold into an XRF machine

An XRF (X-ray fluorescence) scanner is a machine used by jewellers to instantly determine a metal’s quality. Due to its high cost, it’s generally not suitable for home use unless you plan to use it frequently. To use it, simply place the metal sample inside the machine, activate it, and wait for the results on the readout.

Buy an acid testing kit for a more precise estimate of gold karat purity

You can purchase a gold testing kit from a jewellery tool supplier. The kit typically includes all necessary materials, such as acid solutions, testing stones, and detailed instructions. Before you begin, carefully read the instructions to understand the process and conduct an inventory of the supplies to ensure everything is available. This will help ensure accurate testing and avoid mistakes during the process.

Place a drop of acid on the notch

To test gold using a gold testing kit, first select the proper needle based on the type of gold you’re testing. Each needle is designed for a specific karat or gold type. Hold the needle tip directly over the notch on the testing stone or metal sample. Push the plunger to release a single drop of acid into the divot. The reaction will help determine the purity of the metal based on how the acid interacts with the sample.

Commonly used gold alloys and their purity levels:

Gold alloys indicate a combination of gold with other metals to enhance durability and alter its appearance. Common alloys include 18k, 14k, and 10k gold. The table below outlines their purity levels:

• 24k gold: 99.9% pure gold
• 22k gold: Approximately 91.7% pure gold
• 18k gold: 75% pure gold
• 14k gold: 58.3% pure gold
• 10k gold: 41.7% pure gold

Visual Inspection 

Hallmarks are essential symbols stamped on gold jewellery to signify purity and authenticity. Examples include “750” for 18k gold and “585” for 14k gold. It’s crucial to recognize standard hallmarks in your country, such as the BIS Hallmarked stamp in India, ensuring you make informed purchases based on gold purity and quality standards.

Testing Methods 

Apart from the various symbols or markings etched on the gold, several methods exist to test your gold for purity. For instance,

Acid Testing 

The nitric acid test is a precise method for assessing gold purity, favoured by professionals. It involves applying nitric acid to the gold alloy and observing the reaction to determine the amount of gold alloyed with other metals. To conduct this test safely, use a testing kit containing nitric acid of different strengths, a test stone, and protective gear like gloves and goggles due to the corrosive nature of the acid.

Step-by-step process of acid testing:

• Rub the gold against the test stone to create a streak.
• Add a drop of nitric acid to the streak.
• Observe the colour change and reaction.
• Compare the result to a colour chart provided with the testing kit.
• Determine the gold’s purity based on the acid’s effect on the streak.

Magnet Test 

The magnet test is a preliminary method to detect non-gold materials in gold items by observing magnetic attraction. Pure gold is non-magnetic, so any attraction to the magnet suggests the presence of impurities or ferromagnetic metals within the item. However, this test alone cannot accurately determine gold purity. If the gold item is attracted to the magnet, it indicates a potential lower purity level due to the inclusion of other metals. Conversely, if there is no attraction, it suggests a higher likelihood of purity, though non-magnetic metals may still be present. For precise determination of gold purity, complementary tests such as acid tests or X-ray fluorescence analysis are necessary. Therefore, while useful for initial screening, relying solely on the magnet test may not provide a definitive assessment of gold purity.

Electronic Gold Testing 

Electronic gold testing utilizes portable devices that assess gold purity based on electrical conductivity. These testers pass a current through the item and measure resistance; pure gold exhibits high conductivity, whereas impurities decrease it. While user-friendly and offering quick results, they may be influenced by surface contaminants or plating, potentially affecting accuracy. Testing multiple spots on the item enhances reliability but for precise measurements, additional testing methods like fire assay or X-ray fluorescence are recommended.

Other Methods for Gold Purity Testing 

Fire Assay Method:

The fire assay method is a sophisticated and precise technique used predominantly in specialized laboratories to determine the purity of gold and other precious metals. Here’s how it works:

Ultrasonic testing:

Ultrasonic testing uses high-frequency sound waves to assess gold purity. It measures density variations and can detect inconsistencies in the gold item.

Density testing:

Density testing measures the density of the gold item and compares it to the density of pure gold. This method requires specialized equipment and is performed in laboratories.

Analysis of Bead:

The bead obtained after cupellation is then analysed to determine its precious metal content, typically gold. This analysis involves weighing the bead and comparing its weight to the weight of the original sample to calculate the percentage of precious metal present.

Calculation of Purity:

Based on the weight and composition of the bead, the purity of the original gold sample can be accurately determined. This method is known for its accuracy but requires skilled technicians and specialized equipment.

Tips for Accurate Gold Purity Assessment

Selecting reliable testing methods: Choose testing methods based on their reliability, convenience, and suitability for your needs. Combine multiple methods for more accurate results.

Seeking professional assistance, if necessary: If you’re unsure about the results or need precise measurements, consult a professional jeweller or laboratory specializing in gold purity testing.

Recognizing potential factors that can affect test results: Be aware that factors like surface contaminants, plating, and the presence of other metals may affect test results. Consider these factors while interpreting the results.

To ensure accurate gold purity testing, maintain consistent lighting, temperature, and cleanliness. These factors minimize variations in test results. However, for the easiest and most reliable assurance of gold purity in 14 kt, 18 kt, or 22 kt jewellery, consider purchasing from reputable jewellers. They provide authentication certificates and guarantee superior quality in materials and craftsmanship, ensuring peace of mind for buyers. This approach simplifies the process and offers confidence in the authenticity and purity of your gold jewellery purchase.