The CIBJO Precious Metals Book is one of the principal volumes within CIBJO's suite of trade standards — collectively known as the Blue Books — and constitutes the authoritative international reference for the nomenclature, minimum fineness thresholds, alloy designations, and marking requirements applicable to precious metals used in jewellery and related articles. Published by the World Jewellery Confederation (CIBJO, from the French Confédération Internationale de la Bijouterie, Joaillerie, Orfèvrerie des Diamants, Perles et Pierres), the Precious Metals Book sits alongside companion volumes addressing diamonds, coloured stones, pearls, coral, and gemmological laboratories, forming a coherent regulatory architecture intended to harmonise trade practice across member nations and protect consumers from misleading or inaccurate metal claims.

Scope and Purpose

The Precious Metals Book addresses four principal metals recognised in international jewellery commerce: gold, silver, platinum, and palladium. For each, the document establishes minimum fineness levels — expressed in parts per thousand — below which a metal may not carry the designation of the pure element in a commercial context. These thresholds reflect longstanding trade conventions and, in many jurisdictions, are mirrored directly in national hallmarking legislation or voluntary certification schemes.

Beyond fineness, the standard governs the terminology applied to surface treatments and composite metal products. Designations such as gold plating, gold filling, gold overlay, and vermeil are each defined with specific technical parameters — including minimum layer thickness and minimum fineness of the applied metal — so that consumers and regulators can distinguish between a solid precious-metal article and one in which precious metal constitutes only a surface coating or a minor proportion of total mass. The prohibition on misleading designations is explicit: a manufacturer may not describe an article as "gold" if it does not meet the relevant fineness threshold, nor may plated articles be described in language that implies solid metal construction.

Fineness Standards for Each Metal

The Precious Metals Book aligns its fineness requirements with the most widely recognised international conventions, while acknowledging that individual member states may apply stricter national standards. The principal thresholds are as follows:

• Gold: The minimum fineness for an article to be designated as gold is generally set at 375 parts per thousand (equivalent to 9 carat in the British and Commonwealth system, or approximately 37.5% gold by mass). Higher recognised finenesses include 585 (14 carat), 750 (18 carat), 916.6 (22 carat), and 999 (fine gold). The standard acknowledges that certain markets — notably France, Italy, and several Middle Eastern countries — apply a higher minimum of 585 or 750.
• Silver: The minimum fineness for silver is set at 800 parts per thousand in the CIBJO framework, though the internationally prominent Britannia standard (958) and sterling standard (925) are specifically recognised and defined.
• Platinum: Platinum articles must meet a minimum fineness of 850 parts per thousand to carry the platinum designation, with recognised grades at 850, 900, 950, and 999. The standard specifies which alloying elements are permissible within platinum alloys at each fineness level, reflecting the technical reality that pure platinum is rarely used in finished jewellery due to its working characteristics.
• Palladium: Palladium, incorporated into the standard following its growing adoption as a jewellery metal in the early twenty-first century, is recognised at minimum finenesses of 500, 950, and 999 parts per thousand.

Surface Treatments and Composite Products

A significant portion of the Precious Metals Book addresses articles that are not composed entirely of a single precious metal. This section is of particular practical importance given the prevalence of gold-plated, gold-filled, and bi-metal products in the mass-market jewellery trade.

Gold plating (also termed gold electroplating or electro-gilding) refers to a thin layer of gold deposited onto a base metal substrate by electrochemical means. The CIBJO standard requires that the layer thickness and the fineness of the deposited gold be disclosed where plating is claimed, and prohibits the use of unqualified precious-metal terminology for plated articles.

Gold filling and gold overlay describe products in which a layer of gold alloy is mechanically bonded — typically by rolling or heat-bonding — to a base metal core. The standard distinguishes these from plated articles on the basis of layer thickness and the proportion of gold by weight relative to total article weight, and requires that the designation be accompanied by the fineness of the gold layer and the weight ratio.

Vermeil — a term with a long history in European silversmithing — is defined as sterling silver (minimum 925 fineness) with a gold plating of minimum specified thickness and fineness. The standard's treatment of vermeil reflects both the term's historical legitimacy and the need to prevent its misapplication to base-metal substrates.

Hallmarking and International Harmonisation

One of the Precious Metals Book's most consequential functions is its role in supporting the harmonisation of hallmarking practice across jurisdictions. Hallmarking — the independent assay and marking of precious-metal articles to certify their fineness — is legally mandated in a number of CIBJO member countries, including the United Kingdom, France, the Netherlands, and several Gulf Cooperation Council states, while remaining voluntary in others, including the United States. The CIBJO standard does not itself constitute a hallmarking law, but it provides a common definitional framework that national legislators and assay offices can reference when drafting or updating their own requirements.

The standard also intersects with the Vienna Convention on the Control of Articles of Precious Metals (the Hallmarking Convention), administered by the International Association of Assay Offices (IAAO), which operates a mutual recognition system for hallmarks struck by member assay offices. CIBJO's fineness definitions are broadly consistent with those of the Hallmarking Convention, facilitating cross-border trade in hallmarked goods.

Revision and Governance

The Precious Metals Book is maintained by CIBJO's Precious Metals Commission, which reviews the standard periodically to reflect developments in manufacturing technology, the emergence of new alloys, evolving regulatory frameworks in member states, and shifts in trade practice. Revisions are subject to approval by CIBJO's General Assembly, ensuring that the standard reflects broad consensus among national jewellery trade associations from across the membership.

Recent revision cycles have addressed topics including the growing use of alternative precious-metal alloys (such as rose gold and grey gold formulations), the treatment of recycled or recovered precious metals, and the increasing prevalence of surface treatments applied by physical vapour deposition (PVD) and other non-electrochemical methods — technologies that did not exist or were not commercially significant when earlier versions of the standard were drafted.

Significance for the Trade

For manufacturers, retailers, and importers, the Precious Metals Book provides a defensible reference point for product labelling and marketing claims. Compliance with the standard — or with national legislation that incorporates its definitions — reduces the risk of regulatory action, consumer complaints, and reputational damage arising from inaccurate metal descriptions. For consumers and independent gemmologists, it offers a transparent framework against which the accuracy of a retailer's claims can be assessed.

The standard's prohibition on misleading designations is of particular relevance in an era of complex supply chains, in which an article may pass through multiple manufacturing stages across several countries before reaching the end consumer. By establishing clear, internationally recognised terminology, the Precious Metals Book contributes to the integrity of the precious-metals trade at every point in that chain.

Further Reading

• CIBJO Blue Books — official repository of current standards (cibjo.org)