Brass is an alloy of copper and zinc, typically composed of 60–90% copper with the balance made up principally of zinc, though minor additions of lead, tin, or aluminium are sometimes introduced to modify workability or corrosion resistance. Its bright yellow colour, which superficially resembles gold, combined with its low cost, ease of fabrication, and capacity for a high polish, has made it one of the most widely used metals in costume jewellery, decorative findings, and jewellery-making tools. It is not classified as a precious metal and carries no hallmarking obligations under standard precious-metal assay regimes.

Composition and Properties

The copper-to-zinc ratio governs both the colour and the mechanical character of brass. Alloys with a higher copper content — sometimes called red brass or rich low brass — tend toward a warmer, more reddish hue, while those with a greater proportion of zinc produce the cooler, brighter yellow associated with yellow brass (typically around 67–70% copper, 30–33% zinc). Common jewellery-grade brass falls broadly within the 65–70% copper range.

• Hardness: Approximately 55–185 HV depending on temper and alloy composition — harder than pure copper but softer than sterling silver.
• Density: Approximately 8.4–8.7 g/cm³.
• Melting range: Roughly 900–940 °C for common jewellery alloys.
• Workability: Excellent; brass is readily cast, stamped, drawn, and soldered, making it economical for high-volume production of findings, chains, and settings.

Tarnish and Skin Reaction

Brass tarnishes readily on exposure to air and moisture, developing a dull, brownish-green patina as the copper component oxidises and reacts with atmospheric sulphur compounds. This is the same chemical process that produces the characteristic verdigris seen on architectural bronze. In jewellery wear, perspiration accelerates tarnish and can cause a greenish or greyish discolouration of the skin — a harmless but cosmetically undesirable reaction caused by copper salts absorbed into surface skin cells. Individuals with a sensitivity or allergy to zinc or copper may experience mild contact dermatitis. These characteristics distinguish brass sharply from precious metals such as gold and platinum, which are chemically inert in normal wear conditions.

Use in Jewellery

Within the jewellery industry, brass occupies a clearly defined tier. It is the standard substrate for a large proportion of costume and fashion jewellery, particularly pieces intended for short-term wear or trend-driven collections where longevity is not the primary consideration. Findings — the small functional components of jewellery construction such as clasps, jump rings, ear wires, and pin backs — are routinely produced in brass, even for pieces that incorporate genuine gemstones or semi-precious materials.

Brass is also the most common base for gold-plated jewellery. A thin layer of gold, typically applied by electroplating, imparts the appearance of a precious-metal piece at a fraction of the cost. The durability of the plating depends on its thickness, measured in microns; trade designations such as gold-filled and gold vermeil have specific regulatory meanings in several jurisdictions and must not be confused with simple gold-plated brass. Vermeil, for instance, requires a sterling silver substrate under most definitions, not brass.

In the lapidary and gemmological workshop, brass rod and sheet serve as tooling material — brass laps are used in certain cutting and polishing operations — and brass is used for display mounts and specimen bases where a warm metallic appearance is desired without the expense of gold.

In the Trade

Reputable fine jewellers and gemmological laboratories do not grade or certify brass-set pieces as fine jewellery. The absence of hallmarking requirements means that buyers of brass-based pieces have no statutory assurance of metal composition, though consumer-protection legislation in many markets requires accurate disclosure of base-metal content. Buyers should be alert to descriptions such as "gold-tone" or "gold-coloured metal," which typically indicate brass or another base alloy rather than any gold content. When a piece is described as gold-plated, the thickness and karat of the plating layer, as well as the substrate metal, should ideally be disclosed.