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Choosing a gold piece of jewelry is far from intuitive. Between karats, alloys, official hallmarks, and the distinction between solid gold and gold-plated jewelry, questions arise long before making a purchase—and often afterward as well. Whether you are looking for an engagement ring, a family heirloom bracelet, or an antique piece of jewelry as an investment, understanding the quality of the gold you are buying will determine both the durability of the piece and its value over time. This guide brings together everything you need to know to buy or authenticate a gold piece of jewelry, from the various gold fineness standards to professional appraisal techniques, including the alloy colors most commonly encountered in antique jewelry shops.

 

Gold Hallmarks: How to Read a Piece of Jewelry’s Identity Card

The hallmark is the first thing to look for when verifying the nature of a piece of jewelry. It is an official mark stamped into the metal (rather than cast) that certifies the purity of the gold. In France, the system is twofold: the maker’s mark identifies the manufacturer, while the assay hallmark, issued by the State after verification by a licensed assayer, certifies the precious metal content.

 

French Gold Hallmarks You Should Know

For jewelry manufactured in France, the most common assay hallmark for 18-karat gold is the eagle’s head, facing left. This is the symbol found on the vast majority of high-quality antique jewelry, from Belle Époque sets to Art Deco creations. For imported jewelry, the owl’s head has served as the official assay hallmark since 1893. Encountering this hallmark does not mean the piece is of lower quality—it simply indicates that it was manufactured outside France.

 

Where to Find the Hallmark Depending on the Type of Jewelry

The location varies according to the piece: on a ring, the hallmark is found inside the band, while on a bracelet or necklace it is generally placed on the clasp. On a pendant or medallion, it is usually stamped on the bail. One important point: an authentic hallmark is always stamped, never cast. A hallmark that appears melted into the metal, without clear relief or definition, should raise suspicion.

To learn more about this topic, our article dedicated to gold hallmarks provides a detailed overview of French and European hallmarking systems.

 

How to Choose Gold Jewelry According to Its Karat Rating

The fineness of gold (expressed in karats or thousandths) indicates the proportion of pure gold contained in the alloy. The higher the fineness, the greater the gold content, and the more the jewelry’s color tends toward a rich yellow hue. However, a higher fineness is not always synonymous with a better choice: it is only one factor among many, depending on the intended use, budget, and aesthetic preference.

 

24-Karat Gold: The Purest, but Not the Most Suitable

24-karat gold, also known as 999 gold or “four nines” gold, is 99.9% pure gold. Its color is a distinctive bright yellow. Paradoxically, it is the least suitable form of gold for everyday jewelry: it is too soft to withstand the mechanical stresses of pieces worn daily. It is mainly found in the form of bullion bars, collectible coins, or certain Asian jewelry (particularly in Thailand and Hong Kong), where metal purity takes precedence over the durability of the setting. The idea that there could be a gold purer than 24 karats is a commercial absurdity: by definition, 24 karats is the maximum.

 

18-Karat Gold: The Benchmark of French Jewelry

18-karat gold, marked 750 (75% pure gold), is the standard of French jewelry and fine jewelry. It is the fineness used by the great maisons of Place Vendôme and is found on the overwhelming majority of high-quality antique jewelry made in France. Its mechanical strength, lasting color, and compatibility with precious gemstone settings make it the preferred choice for engagement rings, wedding bands, and jewelry intended to become family heirlooms.

 

From 14-Karat to 9-Karat Gold: Legal Standards with Official Hallmarks

Lower fineness standards are entirely legal, carry their own official hallmarks, and in no way imply poor craftsmanship. Fourteen-karat gold (585) predominates in Central European, North American, and Turkish jewelry. Nine-karat gold (375) is especially common in British jewelry. The precious metal content is simply lower, which correspondingly reduces the intrinsic value—an important consideration when purchasing or reselling a piece.

Here is a reminder of the main numerical hallmarks corresponding to common gold fineness standards: 

•  750: 18-karat gold (75% pure gold), the French reference standard

•  585: 14-karat gold, widely used in Central Europe and the United States

•  500: 12-karat gold, less common, found in certain antique pieces

•  375: 9-karat gold, a British specialty and a common standard for quality fashion jewelry

•  333: 8-karat gold, the lowest legal standard recognized in European jewelry

 

Solid Gold or Gold-Plated Jewelry: A Distinction That Changes Everything

The confusion between solid gold and gold-plated jewelry is probably the most common misunderstanding among inexperienced buyers, and it has direct consequences on a piece’s value.

 

How to Recognize Solid Gold Jewelry

A solid gold piece of jewelry is made from a gold alloy throughout its entire thickness, from the outer surface to the core. It retains its luster indefinitely, without discoloring or leaving marks on the skin. It can be worn continuously—while showering, sleeping, or exercising—without its surface deteriorating. This is its main practical advantage, often underestimated at the time of purchase.

 

Gold-Plated Jewelry: What to Know Before Buying

A gold-plated piece of jewelry is made from a base metal—most often copper, bronze, or tin—covered with a thin layer of gold through an electroplating process. By regulation, this layer must be at least 3 microns thick. Over time, the coating wears away and eventually reveals the underlying metal, which is usually lighter in color or slightly greenish. Quality gold-plated jewelry carries a specific hallmark: a recessed square mark identifying the manufacturer. The absence of any hallmark should be considered a warning sign.

 

Gold Alloys and Colors: What Are the Differences?

The color of a gold piece of jewelry depends entirely on the composition of its alloy—that is, the metals added to pure gold to provide hardness and color. Even when the fineness remains constant at 18 karats, the proportions vary according to the desired effect.

 

Yellow Gold, Rose Gold, and White Gold: The Three Great Classics

Yellow gold 18-karat contains 75% gold, 12.5% silver, and 12.5% copper. This is the most traditional formulation and defines the warm, rich color that people instinctively associate with gold. Rose gold owes its coppery tones to a higher copper content (around 22.5%) and a lower proportion of silver. White gold combines gold with palladium or silver and is finished with a rhodium plating that gives it its bright silvery appearance. In the past, nickel was often used instead of palladium, but this practice is now prohibited in Europe because of the risk of allergic reactions.

 

Red Gold, Green Gold, and Blue Gold: Rare Alloys

Red gold (75% gold and 25% copper) is particularly prized in antique Russian and Ottoman jewelry. Green gold combines only gold and silver, without copper, giving it a slightly cool-toned hue. Blue gold and purple gold, which incorporate metals such as cobalt, iron, or aluminum, are rare alloys found mainly in contemporary high jewelry and certain collector’s pieces. These unusual colors demonstrate the nearly limitless possibilities available to master goldsmiths when they fully understand the chemistry of their alloys. The Gemological Institute of America (GIA), the world’s leading authority in gemology, documents the influence of alloy composition on the mechanical and visual properties of gold.

 

Gold Authenticity: Methods to Know for Sure

The question of authenticity inevitably arises when purchasing antique jewelry from a private seller, at a flea market, or during an auction. Several methods can be used to determine whether a piece is genuine, although their reliability varies considerably.

 

The Touchstone and Acid Test: The Professional Method

The most widely used technique among professionals involves rubbing the jewelry against a touchstone (a smooth black testing stone) to leave a metallic streak, then applying different acid solutions to the mark. The chemical reaction—or lack thereof—reveals both the nature of the metal and its fineness. This method requires neither sophisticated equipment nor laboratory facilities: an experienced jeweler or gemologist can usually provide an answer in less than five minutes. This is the type of testing referred to here, not the bite test discussed below.

 

X-Ray Fluorescence: The Gold Standard for Valuable Pieces

For high-value jewelry or gemstone-set pieces, X-ray fluorescence spectrometry (XRF) is the preferred reference method. Non-destructive and accurate to a fraction of a thousandth, it allows experts to determine the exact composition of an alloy without altering the piece in any way. Major appraisal firms, including those working with auction houses such as Drouot, rely on this technology for collectible jewelry.

 

The Bite Test: A Myth That Should Be Put into Perspective

 

 

The image of athletes biting their gold medals is well known. The idea behind it is not entirely unfounded: the purer the gold, the more malleable it is, and a firm bite can indeed leave a mark on pure gold. However, this test is among the least reliable methods available and, more importantly, it irreversibly damages the jewelry. That fact alone should be enough to discourage anyone from attempting it.

 

Antique Gold Jewelry: Additional Factors to Consider

Choosing an antique gold piece of jewelry involves the same criteria as selecting a new one, with the addition of factors specific to the pre-owned and collectors’ market.

 

Heritage Value Beyond Intrinsic Value

An antique 18-karat gold piece is worth far more than the value of its metal alone. The period in which it was made has a significant influence on its price, as do its style—whether it is an Art Deco, Belle Époque, or 1940s–1950s creation—its maker’s signature or association with a renowned jewelry house, and its overall state of preservation. A ring bearing the hallmark of a recognized workshop may be worth several times the value of its gold content. If the heritage and investment dimension of such a purchase interests you, our article on investing in antique jewelry explores the subject in greater detail.

 

The Importance of Expert Appraisal Before Purchase

For a valuable antique piece of jewelry, obtaining an appraisal from a gemologist or a specialized jeweler before purchasing is a basic precaution. Such an evaluation confirms the fineness of the metal, identifies any repairs or modifications, and, in the case of gemstone-set jewelry, assesses both the quality and nature of the stones. In Paris, the specialists of the Village Suisse offer this type of guidance within a transparent market environment, where the provenance of many pieces can generally be traced and documented.

 

Do you own a piece of jewelry whose composition you would like to identify, or are you looking to acquire an antique gold piece in Paris? Les Pierres de Julie offers a complimentary appraisal upon presentation of the item in-store or by sending photographs to contact@lespierresdejulie.com. The boutique is located in the Village Suisse, 1 avenue Paul Déroulède, in Paris’s 15th arrondissement.

 

Where to Find Quality Antique Gold Jewelry in Paris?

Paris remains one of the best places to purchase antique gold jewelry, thanks to the auction houses around Rue Drouot, the antique dealers of Le Marais, and the galleries of the Village Suisse in the 15th arrondissement. Whether you are searching for an everyday piece or a collector’s item, the criteria remain the same: a clearly legible hallmark, a verified fineness, and properly documented authenticity. Antique gold jewelry possesses one advantage that no newly made piece can replicate—it has already stood the test of time.