Platinum is almost as ductile as gold and silver, but it’s harder to scratch than either. It dents more easily than gold, but it’s harder to dent than silver. Platinum takes a high polish, and it’s highly resistant to tarnish. It’s a little denser than gold and more than twice as dense as silver. Its density gives it strength and a heavier feel than the other metals. It’s also less brittle than gold alloy, so platinum prongs are less likely to break. This combination of properties gives platinum durability and makes it an excellent jewelry metal.
Most platinum rates 900 or 950 on the fineness scale. The other 50 or 100 parts in a platinum alloy are often another platinum group metal, usually iridium or ruthenium, added to increase hardness. Cobalt and copper are other metals commonly used in platinum alloys.
Platinum is sometimes plated with rhodium to give it a whiter finish. Plating involves covering a metal with a thin coating of another metal, using an electrical or mechanical process. Plating a metal can protect its surface, enhance its appearance, or change its color.
Like platinum, palladium is a lustrous silvery white metal. The two metals have similar properties, but palladium is not as dense as platinum. It’s been used in jewelry since the 1930s but has caught on with consumers only recently. Palladium can be alloyed with gold to produce white gold, but the alloy is more expensive than conventional alloys using nickel and silver.
