Platinum is a noble metal prized in fine jewelry for its natural bright-white color, exceptional density, and durability. This metal is often considered an ideal choice for sensitive skin because, unlike white gold, it does not require nickel or rhodium plating to achieve its desired appearance. Since platinum is rarely used in its pure form, consumers often ask whether the alloys used to make it suitable for jewelry contain nickel. The presence of nickel depends entirely on the specific formula used when the platinum is alloyed, and standards vary based on the country of manufacture.
Platinum Purity and Alloying Standards
Pure platinum, designated as Pt999, is too soft for the everyday wear and intricate settings required in modern jewelry. This softness would allow prongs to bend easily and surfaces to scratch and deform excessively. To increase the metal’s durability, hardness, and workability, manufacturers introduce small amounts of other metals, a process known as alloying.
Jewelry industry standards define platinum purity by the percentage of pure platinum present in the final alloy. In the United States and the United Kingdom, common commercial standards for platinum jewelry are Pt950 and Pt900. Pt950 indicates that the metal is 95% pure platinum, with the remaining 5% consisting of the alloying metals. Similarly, Pt900 contains 90% pure platinum and 10% alloy.
The choice of alloying metal significantly influences the final properties of the piece, such as its hardness and suitability for casting or fabrication. The remaining percentage of the alloy is where the potential for nickel lies. These standards ensure the consumer knows the precise platinum content, but not necessarily the exact composition of the remaining alloy.
Common Alloying Metals Used with Platinum
The metals chosen for platinum alloys fall into two main categories based on the properties they impart: hard and soft alloys. Iridium, a metal from the platinum group, is often used to create a softer alloy, such as a Pt950/Ir50 mixture, which is easier to work with for intricate hand-fabricated pieces. Ruthenium, another platinum group metal, creates a harder, more ductile alloy like Pt950/Ru50, which is commonly used in casting and provides greater resistance to scratching and wear.
Other metals are also used, including cobalt, which creates a very hard alloy (Pt950/Co50) that is excellent for casting fine details but is slightly magnetic. Copper is also sometimes used, particularly in Europe, for general-purpose alloys. Historically, nickel was used as an alloying agent in some regions due to its hardening properties, and it remains a component in non-jewelry industrial platinum alloys.
In contemporary jewelry from the US and UK, nickel is generally avoided in platinum alloys due to consumer demand for hypoallergenic products and the prevalence of nickel sensitivity. The vast majority of high-purity platinum jewelry uses other platinum group metals to achieve the necessary hardness and workability. If nickel is present, it is most often found in lower-purity platinum alloys or in components like solder used for repair or white gold findings attached to the platinum piece.
Understanding Nickel Sensitivity and Platinum Jewelry
The primary concern regarding nickel in jewelry is the risk of allergic contact dermatitis. This reaction is a delayed-type hypersensitivity where the skin develops a rash, itching, or redness upon prolonged contact with nickel-releasing metals. Even a small amount of nickel can trigger a reaction in individuals who have become sensitized, a condition estimated to affect about 10% of the Western population.
The European Union established strict regulations to protect consumers from this health risk, initially through the Nickel Directive, which is now incorporated into the REACH regulation (Regulation EC No 1907/2006). This regulation restricts the amount of nickel that can be released from jewelry that comes into direct and prolonged contact with the skin. Specifically, the limit is set at 0.5 micrograms per square centimeter per week for items like rings and necklaces.
Although the United States lacks a federal nickel-specific law for jewelry, the EU’s strict standards have influenced global manufacturing practices. Consequently, most reputable jewelers worldwide use platinum alloys that are intentionally formulated without nickel to ensure compliance and meet the expectation of a hypoallergenic product. Consumers with a known nickel allergy should still be diligent, as the greatest risk of nickel exposure in a platinum piece often comes from a non-platinum component, like a white gold clasp or a low-quality solder used in construction or repair.
Identifying Platinum Hallmarks and Stamps
Consumers can gain insight into a piece’s composition by examining its hallmark or stamp. This is a set of markings engraved onto the metal, typically on an inconspicuous surface like the inside of a ring shank. The hallmark’s primary function is to denote the percentage of pure platinum present in the alloy. Common stamps include “Pt950,” which signifies 95% pure platinum, and “Pt900,” which indicates 90% purity.
Other variations include “PLAT,” “PLATINUM,” or the millesimal fineness number alone, such as “950.” In regions like the UK, hallmarking is a legal requirement where the piece is tested by an independent assay office before the mark is applied, guaranteeing its purity.
While these marks confirm the high platinum content, they generally do not specify the exact alloying metal used. For example, a “Pt950” stamp does not differentiate between an alloy of platinum/iridium and one of platinum/ruthenium. If a consumer has a severe nickel allergy and requires absolute certainty, they should ask the jeweler for written confirmation of the alloy breakdown. This step is particularly important for antique or foreign-made pieces where the alloy standard may be less consistent with modern hypoallergenic practices.