The question of whether platinum is softer than gold is common, and the answer depends entirely on the metal’s purity. Both Platinum (Pt) and Gold (Au) are highly valued precious metals used in fine jewelry. When comparing the two elements in their pure, unmixed state, a clear scientific difference emerges in their resistance to deformation. However, commercial jewelry is almost never made from pure metal, and the addition of other elements dramatically alters the final material’s properties. Understanding how hardness is measured and how alloying works is necessary to compare the durability of these two metals in a wearable item.
Defining Hardness in Precious Metals
In materials science, “hardness” refers to a metal’s resistance to localized permanent deformation, such as scratching, indentation, or abrasion. This metallurgical definition differs from the common consumer understanding of “durability,” which often refers to overall longevity. Hardness is typically measured using two main methods: the Mohs scale and the Vickers scale.
The Mohs scale is a qualitative measure of scratch hardness, ranking materials based on their ability to visibly scratch one another. A higher number indicates greater scratch resistance. The Vickers scale is a quantitative measure of indentation hardness, determined by pressing a diamond-shaped indenter into the material surface and measuring the resulting impression. For precious metals used in jewelry, resistance to permanent deformation is the practical metric, as it relates directly to how well the material maintains its shape and surface finish.
Comparing Pure Platinum and Pure Gold
When strictly comparing the pure elements, platinum is measurably harder than gold. Pure 24-karat gold (100% gold) registers a very low score of about 2.5 on the Mohs scale. This makes it one of the softest metals used in jewelry, meaning it is easily scratched and dented.
Pure platinum, in contrast, is significantly harder, typically scoring between 3.5 and 4.5 on the Mohs scale. This difference is also reflected in quantitative indentation tests. Pure platinum exhibits a Vickers hardness value ranging from approximately 400 to 549, while pure gold is much lower, generally between 188 and 216 Vickers. Therefore, at the elemental level, platinum is substantially more resistant to scratching and indentation than gold.
The Practical Impact of Alloying on Jewelry Durability
The raw hardness values of the pure metals change dramatically once they are mixed with other metals to create jewelry alloys. Gold is almost always alloyed to increase its strength and durability. Common forms include 14-karat gold (58.3% gold) and 18-karat gold (75% gold). The remaining percentage consists of hardening agents like copper, silver, or nickel, which significantly increase the metal’s overall hardness. For example, 14-karat gold alloys can reach a Mohs hardness of 3.0 to 3.5, placing them in a range comparable to, or even slightly harder than, many platinum alloys.
Platinum jewelry is held to a much higher standard of purity. The most common alloy is 950 platinum (95% pure platinum and 5% other metals, often iridium, ruthenium, or cobalt). Because platinum is used at a much higher purity, the resulting alloy is often still softer than the most common gold alloys. While the gold alloy is typically harder and more scratch-resistant initially, the way the two metals wear creates a major practical difference in durability.
When a gold alloy piece is scratched, a tiny amount of metal is physically removed from the surface, resulting in material loss and a visible scratch. Over decades of wear, this gradual material loss can thin the prongs holding gemstones and reduce the piece’s weight.
Platinum, due to its density and unique molecular structure, behaves differently when scratched. Instead of the metal flaking away, it is merely displaced or pushed aside, creating a microscopic ridge sometimes referred to as a patina finish. This metal displacement means that, over time, a platinum piece retains its original volume and weight, maintaining the structural integrity necessary to securely hold gemstones. While a platinum ring may show more surface scratches and a duller finish than a gold ring of similar hardness, a professional polishing can easily push the displaced metal back into place, restoring the original sheen with minimal material loss. This characteristic is why platinum is often considered the superior choice for gemstone settings, as its wear pattern ensures long-term security and structural strength.