We know that gold is a symbol of wealth, tradition, and elegance. But are all the gold pieces we see actually made of gold?
Often, plated or gold-plated jewelry goes unnoticed as "real gold," and only later does disillusionment set in.
In this article, you'll learn how to assess the authenticity of gold, from simple tests you can perform at home to the essential role of the Assay Office in Portugal.

Gold is one of the most sought-after precious metals in the world, associated with value, elegance, tradition, and a safe investment. But precisely because it is so highly valued, it is also the target of imitations, fraud, and confusion. Many people have inherited jewelry at home, purchased in jewelry stores, at fairs, or even received as gifts, but are unsure whether it is real gold or simply plated, plated, or even fake.

Knowing how to identify the authenticity of gold is essential to ensure the security of your investment and confidence in daily use. In this comprehensive article, you'll learn:

• The difference between real, plated, and gold;
• Home tests that help verify if jewelry is truly gold;
• The importance of official hallmarks and the Portuguese Assay Office;
• Professional gold appraisal methods;
• Tips for buying jewelry with confidence and avoiding counterfeits.

Shall we explore each point in detail together?

What is real gold?

Before we talk about testing, it's important to understand the concept of real gold.

• Solid gold (or true gold): means that the jewelry is made entirely of gold in a specific metal alloy.
• Pure gold (24K) is too soft for use in jewelry, so it is mixed with other metals to increase its strength. This results in 9K, 14K, 18K, or 19.2K (Portuguese standard) alloys.
• Gold-plated: The piece is composed of a base metal (such as copper or brass) and coated only with a thick layer of gold. It resists wear longer than plated pieces, but it is not solid gold. Gold-plated (or "gilded"): This is the most common and affordable version. The jewelry receives only a very thin layer of gold applied by electroplating. Over time, the layer disappears, revealing the base metal.

Only solid gold maintains eternal value and durability. In other words, a piece of jewelry can shine like gold without actually being so. Therefore, it becomes essential to learn to distinguish.

Home Tests to Determine if It's Real Gold

There are several simple methods anyone can use before consulting a professional. It's important to remember that no home test is 100% conclusive, but they all provide a good initial indication. Note, however, that these methods can be performed at home to raise suspicions, but they are not a substitute for official certification.

1. Look for the Hallmark

The most practical and reliable way is to check if the piece has an official hallmark. In Portugal, the Hallmark certifies all gold and silver jewelry by placing a small mark (usually on the inside of the band or clasp).

• Example: "375" (9K gold), "585" (14K gold), "750" (18K gold), or "800/999" in rare cases.
• Jewelry in 19.2K Portuguese gold bears the mark "800" (800 thousandths).

If the piece doesn't have a stamp, it could be a sign of counterfeiting, but be careful: very old or handmade pieces may not have a mark. 

2. Magnet Test

Gold is a non-magnetic metal.

• Approach a powerful magnet to the jewelry.
• If the piece is attracted, it's probably not gold, but steel or another base metal.

⚠️ Caution: Some alloys may contain small amounts of magnetic metals and cause a slight attraction. This test is useful, but not definitive.

3. Density Test

Gold is one of the densest metals (19.3 g/cm³).

• Weigh the jewelry on a precision scale.
• Measure the volume (by placing the piece in water and observing its displacement).
• Divide the weight by the volume: if the value is close to 19.3, there's a good chance it's genuine gold.

This test is more scientific, but requires care and precise measuring equipment.

4. Ceramic Test

• Run the jewelry over an unglazed ceramic plate.
• Real gold leaves a golden streak.
• Faux metals leave a black, gray, or greenish streak.

⚠️ Caution: This test may slightly scratch the piece.

5. Nitric Acid Test

This is one of the most commonly used methods by appraisers:

• Place a drop of nitric acid on the piece.
• If there is a reaction (corrosion, foaming, or color change), it is not real gold.
• Solid gold does not react to acid.

⚠️ Not recommended for home use without protection, as the acid is dangerous.

6. Skin Test (Oxidation Test)

When worn on the skin, real gold does not tarnish.

• If, after some time of wear, the jewelry leaves the skin greenish or dark, it is likely plated or fake.
• Genuine gold maintains its shine and does not oxidize.

Assay Office in Portugal: The Official Guarantee

In Portugal, there is a major advantage: the official Assay Office system, which guarantees the authenticity of precious metals.

All gold, silver, platinum, or palladium jewelry must be analyzed and hallmarked, and bear the official seal certifying its purity.
The Assay Office uses an official seal (mark) that certifies the purity of the metal.
Examples of hallmarks:

• 375 → 9K Gold
• 585 → 14 Gold
• 750 → 18 Gold
• 800 → 19,2 Gold (Portuguese gold)

In addition to the hallmark, jewelry must also display the manufacturer's mark and may also have the goldsmith's mark.
This system protects the consumer, as this is the only way to be certain of the jewelry's authenticity and purity.
When purchasing jewelry, always demand hallmarks. It is the only legal and guaranteed way to prove the authenticity of the gold.

Professional Appraisal Methods

In addition to home testing, a professional appraiser or goldsmith can use more precise technical methods for a definitive appraisal using advanced techniques such as:

•  XRF (X-ray Fluorescence) → Identifies the exact composition of the metal without damaging the piece.
• Fire Assays → Traditional technique that involves melting a small sample to analyze purity.
• Hydrostatic Density Machines → Measure density with absolute precision.

These methods are used in jewelry stores, gold shops, and auctions to ensure the complete authenticity of pieces.

Tips for buying gold safely

• Always buy from authorized jewelry stores.
• Require a receipt and certificate for the piece.
• Check the official hallmark before purchasing.
• Be wary of prices that are significantly below market value: gold isn't cheap.
• When in doubt, take the piece to a trusted goldsmith or assay office.

Discover Authentic Gold Jewelry

At Lusijoia, we only work with certified jewelry in 19.2K Portuguese gold and other real gold. Each piece has an official hallmark, ensuring authenticity, value, and elegance.

Explore our gold collection.
Or, if you have jewelry in storage, seize the moment: we'll buy your gold with a fair and immediate appraisal and pay you immediately.

Conclusion

Knowing if a piece of jewelry is real gold may seem difficult, but with the right information, it becomes simple.
Remember that identifying whether a piece of jewelry is real gold is essential to protecting your investment.

• Home tests, such as magnets, ceramics, or hallmarks, can help give you a first idea.
• However, the only completely reliable way in Portugal is to verify the official hallmark of the Assay Office.
• For those who buy or sell gold, this knowledge is essential to avoid fraud and increase the value of the piece.

Gold, due to its rarity and value, will continue to be an investment and traditional jewel. But only genuine gold preserves its eternal shine.
Gold is eternal – but only when it's real!

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