9 Ways to Test Your Gold Coins

📌 Note: This is a long article and takes about 10 minutes to read. It also assumes some basic knowledge of physics and chemistry. If you're short on time, feel free to skip to the comparison table at the end for a quick summary, and take a closer look at any specific method if needed.

Ensuring the authenticity of gold coins is essential for both collectors and investors. A wide variety of testing methods are available, each with its own strengths and limitations.

In this article, we explain how they work, show how to do the tests, and compare them based on a few key points after a comprehensive evaluation of these methods.

• In-depth: Whether the test examines only the surface or penetrates deeper layers
• Quantitative result: Whether the method provides a measurable purity result
• No-damage: Whether the method is non-destructive or alters the coin
• Practicality: Ease of use and cost-effectiveness
• Fails-on: Types of counterfeit coins that the method fails to detect. Since counterfeit variations are virtually limitless, an exhaustive list isn't feasible. Instead, we highlight known failure cases based on the underlying mechanism of each test.

Let's begin with the simplest method and move toward the more advanced ones.

1. Weight and Dimensions Measurement

Authentic gold coins have well-defined weight and dimensions. Measuring these can help identify discrepancies. This method is generally easy to perform, non-destructive, and requires only basic instruments. However, weight and size are not intrinsic material properties. Counterfeiters can manufacture coins from base metals that mimic the correct weight and diameter. While measuring thickness can improve accuracy and yield results similar to the Specific Gravity method discussed later, it is often challenging due to the coin's relief and surface irregularities.

• In-depth: ❌ (not relying on material property)
• Quantitative result: ❌
• No-damage: ✅
• Practicality: Easy and cheap
• Fails-on: Counterfeit coins with the correct weight and size

2. Magnet Attraction Test

There are two types of magnet-based tests. Here, we focus on the Magnet Attraction Test. The other, commonly referred to as the Magnet Sliding Test, will be discussed later.

How it Works

Gold is non-magnetic. If a coin is attracted to a magnet, it is definitely not made of gold. The Magnet Attraction Test is effective for detecting coins with ferromagnetic core materials. However, it cannot detect counterfeits made from non-magnetic metals such as copper or tungsten, which can easily pass this test.

• In-depth: ✅ Detects internal ferromagnetic materials
• Quantitative result: ❌
• No-damage: ✅
• Practicality: Easy and cheap
• Fails-on: Non-ferromagnetic fakes (e.g., copper, tungsten)

3. X-Ray Fluorescence (XRF) Spectrometry

XRF spectrometry uses X-rays to analyze the elemental composition of a coin.

How it Works

When high-energy X-rays are directed at a metal surface, the atoms in the metal absorb that energy and then emit their own secondary X-rays. These emitted X-rays have specific energies that are unique to each element. By detecting and measuring these energies, an XRF device can accurately identify which metals are present and in what proportions.

Because this method is based on atomic properties, it provides highly precise measurements of the metal's composition. However, XRF mainly tests only the surface of the coin. The actual depth depends on the energy of the device, but typically no deeper than about 50 micrometers (0.0005 mm). While the incoming X-rays do penetrate deeper, the emitted X-rays from lower layers are often reabsorbed before reaching the detector. This means that XRF may miss counterfeit coins that are gold-plated over a different metal core.

XRF machines are easy to use but often expensive, starting from around $1000 for basic models, and more expensive for professional-grade devices.

• In-depth: ❌
• Quantitative result: ✅
• No-damage: ✅
• Practicality: Easy but costly
• Fails-on: Gold-plated counterfeits

4. Sound Test (Ping Test)

The Ping Test relies on the sound produced when a coin is tapped to distinguish genuine coins from counterfeits.

How it Works

Metals vibrate when struck, producing sound. The sound generated depends on the shape of the metal and how the metal atoms are bonded together. This means the sound is an intrinsic property of the metal itself. In other words, different metals will generate different sounds when in the same shape. The Ping Test uses this principle to determine if a coin is made of gold.

Traditionally, the Ping Test requires a lot of experience and relies on the tester’s ear, and knowledge on different coins. Luckily, modern versions of the test use computer algorithms to analyze the sound, making the process more precise and consistent. There is no universal standard for how these results are calculated, and each system returns results based on its own algorithm. Therefore, precision can vary significantly between different applications.

As a final note, this method requires precise input of coin's shape because the sound depends on it too. Using wrong shape parameters can make the test results meaningless.

• In-depth: ✅
• Quantitative result: Depends on the application; some systems provide quantitative results, while others are more qualitative
• No-damage: ✅ Non-destructive
• Practicality: Easy and cheap, but accuracy may depend on the quality of the equipment or tester's experience
• Fails-on: Counterfeits made of the same material

Since the quality of the test largely depends on the specific application, making a wise choice is very important. Please check out a detailed review article on existing Pint Test apps.

5. Electronic Gold Testers

These devices rely on electrical conductivity to distinguish gold from other materials.

How it Works

Gold is a good electrical conductor with a conductivity of 44.2 million S/m. It ranks third among metals, after silver (63.0 million S/m) and copper (59.6 million S/m). Electronic gold testers typically use an electrical current to measure the material’s resistance, which is inversely related to its conductivity. The tester evaluates how well the coin conducts electricity, which helps determine whether the material is gold or another metal.

While the method is non-destructive, it can sometimes be deceived because metals like copper and silver have higher conductivity than gold. Alloys made from these metals can have a conductivity close to that of gold, and thus may pass the test despite not being genuine gold.

These devices are highly specialized and often expensive. One of the most popular models is the Sigma Metalytics.

• In-depth: ✅
• Quantitative result: ❌
• No-damage: ✅
• Practicality: Easy but costly
• Fails-on: High-conductivity fakes (copper, silver, etc.)

6. Magnet Sliding Test

Slide the coin down a strong magnet. Real gold will slide slowly.

How it Works

Gold is an excellent electrical conductor. When a conductive material like gold moves through a magnetic field (or when a magnet moves across it), eddy currents are induced in the metal. These currents create their own magnetic field that opposes the motion of the magnet, producing a damping effect. This is a consequence of Lenz's Law.

In the Magnet Sliding Test, if you tilt a strong magnet and place a gold coin at the top, the coin will slide down slowly due to this electromagnetic damping. This behavior is characteristic of conductive, non-magnetic metals like gold.

However, this method is not definitive. Other high-conductivity, non-magnetic metals like copper and silver may show similar results. Also, interpreting the sliding speed requires experience, making the test somewhat subjective.

• In-depth: ✅
• Quantitative result: ❌
• No-damage: ✅
• Practicality: Moderate difficulty, depending on experience but cheap
• Fails-on: High-conductivity fakes (e.g., copper, silver)

7. Specific Gravity Test

Each material has a unique specific gravity: the ratio of its density to the density of water. This property can help determine whether a coin is made of gold or another material.

How it Works

You can perform a Specific Gravity Test at home using a high-precision scale, a cup of water, and a bit of patience.

1. Weigh the coin in air and record the weight as W.
2. Fill a cup with water, place it on the scale, and reset (tare) the scale to zero.
3. Suspend the coin using a thin string and fully submerge it in the water without touching the sides or bottom. Record the apparent weight of the coin while submerged. This is the weight of the displaced water, denoted as W0.
4. Calculate the specific gravity using the formula:
   Specific Gravity = W / W0

Gold has a specific gravity of approximately 19.3. If the measured value is significantly lower, the coin is likely not pure gold.

However, one common counterfeit material, tungsten, has a very similar specific gravity (~19.25), making it difficult to detect using this method alone. This test is best used in conjunction with other methods for increased reliability.

• In-depth: ✅ Tests the bulk density of the coin
• Quantitative result: ❌
• No-damage: ✅
• Practicality: Moderate difficult and cheap
• Fails-on: Tungsten-based counterfeits

8. Acid Test

The Acid Test is a common method used to assess the purity of gold by applying nitric acid to a small scratch on the coin. The reaction, or lack thereof, provides an indication of the gold's purity.

How it Works

Gold is highly resistant to most acids, including nitric acid. However, base metals commonly mixed with gold, such as copper and silver, react with nitric acid. When the acid is applied to a small scratch on the coin, it will dissolve the base metals, but not the gold itself. This allows for a distinction between pure gold and lower-purity gold alloys, or gold-plated counterfeits.

Pure gold (24K) does not react to nitric acid, while lower-purity gold (e.g., 18K or 14K) will show signs of reaction due to the presence of other metals. For example:

• 24K gold (pure gold) remains unaffected by nitric acid.
• 18K gold (75% gold) will show a mild reaction because of the other 25% of base metals.
• 14K gold (58.3% gold) will produce a stronger reaction due to the higher percentage of base metals like copper.

Gold-plated items may show a strong reaction when the acid reaches the base metal beneath the gold layer, confirming the item is not solid gold. However, if the gold plating is thick, the acid may not penetrate it easily, which can lead to a false result.

The reaction often leads to visible color changes or bubbling, which can be used to estimate the gold's purity. However, this test is destructive, leaving a visible mark on the coin or jewelry.

• In-depth: ❌
• Quantitative result: ❌
• No-damage: ❌
• Practicality: Can be dangerous but cheap
• Fails-on: Thick gold-plated counterfeits

9. Fire Assay / Potentiometric Titration

The Fire Assay method (also known as Cupellation) is the traditional gold purity testing technique. This method requires a significant amount of material to conduct the test. Modern methods such as Potentiometric Titration require much less material and offer a reliable alternative to traditional fire assays.

Both methods are highly accurate and provide quantitative results, but they are destructive and require specialized equipment, making them impractical for everyday use. Despite this, they are regarded as the gold standard for determining gold purity.

How it Works

Fire Assay: In the traditional fire assay method, the coin is heated to extremely high temperatures in a furnace, typically around 1,100°C (2,012°F), causing the gold to separate from other metals in the coin. The gold is then measured and analyzed to determine its purity. This method is highly accurate but requires a large sample of the material and is destructive, making it impractical for high-value items.

Potentiometric Titration: Potentiometric Titration, a more modern and less material-intensive technique, involves dissolving the gold sample in an appropriate solvent to create a gold solution. An electric current is passed through the solution, and the potential difference between two electrodes is measured as a titrant (a substance added to the solution) is slowly introduced. This allows for precise measurement of the gold content in the sample. Though it requires less material, it still destroys the sample, making it less desirable for coins or artifacts that are valuable or collectible.

• In-depth: ✅
• Quantitative result: ✅
• No-damage: ❌
• Practicality: Difficult and expensive
• Fails-on: Counterfeits made of the same material

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Comparison Table

Our Recommendation

Among all the methods discussed, the most effective non-destructive options are the Sound (Ping) Test, Electronic Gold Tester, and Magnet Sliding Test. These three techniques leverage the intrinsic physical properties of gold, such as its conductivity and atomic structure, making them reliable tools for detecting counterfeits.