Platinum Group Metals
The Stillwater Mine in Montana Produces PGMs
Platinum (chemical symbol Pt) is a silvery-gray metal, one of six that comprise the platinum group metals, or PGMs. The other PGMs are iridium (Ir), osmium (Os), palladium (Pd), rhodium (Rh), and ruthenium (Ru). Platinum is the most abundant of the PGMs. When the other PGMs are found, they are almost always alloyed with platinum or a component of platinum ore.
When measured in parts per billion of the Earth’s crust, platinum is more abundant than gold, but it is more dispersed and more difficult to refine, so it commands a higher price.
In the Future, Platinum Could be Harvested from Asteroids
Platinum is 27 times more abundant in meteorites than it is on Earth. Scientists speculate that an asteroid half a mile in diameter could potentially contain as much as 7,500 tons of platinum. Given the price of the metal today, fortunes would be made if it could be harvested from space.
Iridium is also found in meteorites, and some scientists believe it holds the clue to the extinction of the dinosaurs. According to experts, a giant asteroid slammed into Earth approximately 65 million years ago, causing a period of mass extinction. All over the world, layers of rock dating to this period contain iridium levels that are thousands of times higher than usual. It is possible that this iridium may have come from the asteroid that killed off the dinosaurs.
Platinum is one of the heaviest materials on Earth. A 6-inch (15 cm) cube of platinum weighs 165 pounds (75 kg), the weight of an average adult male.
Platinum is highly malleable and ductile, although less so than gold. Of the “big three” precious metals—gold, silver, and platinum—platinum has the least metal memory. This is a good characteristic in jewelry making. It means that once platinum is bent into new shape, it tends to retain that new shape.
Queen Alexandra
Platinum is also very dense, which lends strength to delicate jewelry designs. The lacy styles of the Edwardian period were created when platinum became a popular metal in the jewelry industry.
Platinum is exceptionally durable. All metals scratch, and platinum is no exception. However, when platinum is scratched, the metal is merely displaced; it does not tend to chip or break off. As a result, scratched platinum jewelry can be repolished with little loss of weight.
World PGM Production in 2008
Rhodium-Plated White Gold
Platinum jewelry is usually made by alloying platinum with other PGMs, usually ruthenium or iridium. Jewelers create platinum alloys because the resulting metal is harder and more lightweight than platinum alone. Platinum, like gold and sterling silver, is often plated with rhodium to produce a shinier, whiter color.
Palladium-Plated Belt Buckle
Palladium is increasingly used in jewelry because it costs less and is more lightweight than platinum. And because it has a lovely color, it does not require rhodium plating. When palladium is alloyed with platinum, it increases platinum’s ductility. Palladium can also be used to alloy gold when a white-gold color is desired.
To date, osmium has seldom been used in jewelry because it is difficult to work and extremely rare. However, new PGM alloys are continually being created, and the future of the platinum group metals is wide open.
