Palladium

Palladium is a soft silver-white metal that resembles platinum. Palladium is far more expensive than silver, yet it is sometimes used to imitate silver in outdoor situations because it does not tarnish. Side by side with silver, palladium is distinctly yellower and darker,  Palladium has the lowest melting point of the platinum group metals. It is soft and ductile when annealed and greatly increases its strength and hardness when it is cold-worked. Palladium dissolves slowly in sulfuric, nitric, and hydrochloric acid. This metal also does not react with oxygen at normal temperatures (and thus does not tarnish in air.). Palladium heated to 800°C will produce a layer of palladium(II) oxide (PdO). It lightly tarnishes in moist atmosphere containing sulfur.

Jewelry

It can also be used as a substitute for nickel when making white gold. Palladium is one of the three most popular metals used to plate gold, making white gold. (Nickel and  silver can also be used.) Palladium-gold is a more expensive alloy than nickel-gold, but it's naturally hypoallergenic and holds its white color better.

When platinum was declared a strategic government resource during World War II, many jewelry bands were made out of palladium. As recently as September 2001, palladium was more expensive than platinum and rarely used in jewelry also due to the technical obstacle of casting. However the casting problem has been resolved, and its use in jewelry has increased because of a large spike in the price of platinum and a drop in the price of palladium.

Prior to 2004, the principal use of palladium in jewelry was as an alloy in the manufacture of white gold jewelry, but, beginning early in 2004 when gold and platinum prices began to rise steeply, Chinese jewelers began fabricating significant volumes of palladium jewelry. Johnson Matthey estimated that in 2004, with the introduction of palladium jewelry in China, demand for palladium for jewelry fabrication was 920,000 ounces, or approximately 14% of the total palladium demand for 2004 - an increase of almost 700,000 ounces from the previous year. This growth continued during 2005, with estimated worldwide jewelry demand for palladium of about 1.4 million ounces, or almost 21% of net palladium supply, again with most of the demand centered in China. The popularity of Palladium jewelry is expected to grow in 2008 as the world's biggest producers embark on a joint marketing effort to promote Palladium jewelry worldwide