Considered the noblest of the precious metals, platinum is also the strongest and hardest. Platinum was first used in jewelry around 1890. Platinum had been in use by the Incas at the time the Spanish
arrived in the new world, but it was not until hotter burning, more modern jeweler's torches were developed that platinum saw use in jewelry. Platinum binds tenaciously to other platinum group metals
(iridium, palladium, ruthenium, osmium, and rhodium), which makes refining platinum more difficult.
Platinum quickly replaced silver as the white metal of choice. It was typical for Victorian jewelry to have a silver top and a gold back. In this way the diamonds could be set in white metal, but the
gold would add value to the piece and keep the silver tarnish off the clothing of the owner. As the Victorian period gave way to the Edwardian period, we see pieces with a platinum top and a gold back.
Platinum was stronger, harder, and didn't tarnish, but because it was not well known, people still insisted on having the gold back.
Gradually pieces made entirely of platinum became the norm. Platinum's hardness allowed a great freedom in jewelry design and very ornate and delicate pieces were produced. Platinum maintained its status
as the preferred white metal until the outbreak of World War II. Owing to platinum's non-jewelry applications, it was designated a strategic metal, and civilian use was prohibited until after the war.
During this time, and for many years afterward, white gold was used a substitute metal.
Platinum's melting point (3224° F) is much higher than gold (1945° F), and it is much more difficult to cast and polish. It requires a different set of tools than gold work requires, and because
of this many modern jewelers prefer to work exclusively in gold.Platinum used in jewelry is a much purer metal than karat gold, and is usually 85% to 99% platinum. The most common metal used to alloy
platinum is iridium, another rare and expensive platinum group metal that makes pure platinum even harder and more durable.
In the U.S. platinum jewelry containing 95% or more platinum is stamped PLATINUM or PLAT. Alloys with 75% to 95% platinum must be stamped with the alloy metal as well (e.g. 10% IRIDPLAT for a 10% iridium
90% platinum alloy). European platinum jewelry is usually a 95% alloy and is stamped PT 950. Some European platinum chains use an 85% alloy and are stamped PT 850.
