These are two more very important and precious elements you might of never heard of.

Palladium has the lowest melting point and is the least dense of the precious metals. When palladium is at room temperature and atmospheric pressure, it can absorb up to 900 times its own volume of hydrogen, which makes palladium an efficient and safe storage medium for hydrogen and hydrogen isotopes. Palladium’s precious metal qualities and appearance generate significant consumption in the luxury jewelry market. Palladium is found in many electronics including computers, mobile phones, multi-layer ceramic capacitors, component plating, low voltage electrical contacts, and SED/OLED/LCD televisions. Palladium is also used in dentistry, medicine, hydrogen purification, chemical applications, groundwater treatment, and it plays a key role in the technology used for fuel cells, which combines hydrogen and oxygen to produce electricity, heat and water.

In addition to mining, recycling is also a source of palladium, mostly from scrapped catalytic converters. The numerous applications and limited supply sources of palladium result in palladium drawing considerable investment interest Palladium was discovered by William Hyde Wollaston in 1803. This element was named by Wollaston in 1804 after the asteroid Pallas, which had been discovered two years earlier. Palladium chloride was at one time prescribed as a tuberculosis treatment at the rate of 0.065g per day (approximately one milligram per kilogram of body weight). This treatment did have many negative side-effects, and was later replaced by more effective drugs.

Palladium’s affinity for hydrogen led it to play an essential role in the Fleischmann-Pons experiment in 1989, also known as cold fusion.

Palladium itself has been used as a precious metal in jewelry since 1939, as an alternative to platinum or white gold. This is due to its naturally white properties, giving it no need for rhodium plating. It is slightly whiter, much lighter and about 12% harder than platinum. Similar to gold, palladium can be beaten into a thin leaf form as thin as 100 nm (1/250,000 in). Like platinum, it will develop a hazy patina over time. Unlike platinum, however, palladium may discolor at high soldering temperatures, become brittle with repeated heating and cooling, and react with strong acids.

Palladium is one of the three most popular metals used to alloy with gold, making white gold. 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.

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 Rhodium is a chemical element with the symbol Rh and atomic number 45. It is a rare, silvery-white hard transition metal and a member of the platinum group, found in platinum ores and is used in alloys with platinum and as a catalyst. It is usually the most expensive precious metal, though it is sometimes surpassed by rhenium, depending on the market.

Rhodium has a high reflectance and does not normally form an oxide, even when heated. Oxygen is absorbed from the atmosphere at the melting point of rhodium, but on solidification the oxygen is released. Rhodium has both a higher melting point and lower density than platinum. It is not attacked by acids: it is completely insoluble in nitric acid and dissolves slightly in aqua regia. A complete dissolution of rhodium in powder form is only obtained in sulfuric acid.

The primary use of this element is as an alloying agent for hardening and improving the corrosion resistance of platinum and palladium. These alloys are used in furnace windings, bushings for glass fiber production, thermocouple elements, electrodes for aircraft spark plugs, and laboratory crucibles.

Other uses include:

• Electrical contact material due to its low electrical resistance, low and stable contact resistance, and its high corrosion resistance.
• Plated rhodium, made by electroplating or evaporation, is extremely hard and is used for optical instruments.
• Jewelry and for decorations. It is electroplated on white gold and platinum to give it a reflective white surface. This is known as rhodium flashing in the jewelry business. It also may be used in coating sterling silver in order to strengthen the metal from tarnish, as a result from the copper compound found in sterling silver.

  Rhodium metal is, as a noble metal, inert. However, when rhodium is chemically bound, it is reactive.

  Rhodium compounds are not often encountered by most people and should be considered to be toxic and possibly carcinogenic. Rhodium compounds can strongly stain human skin. The element plays no biological role in humans.

  If used in elemental form rather than as compounds, the metal is harmless. Rhodium has been used for honours, or to symbolize wealth, when more commonly used metals such as silver, gold, or platinum are deemed insufficient.

  In 1979 the Guinness Book of World Records gave Paul McCartney a rhodium-plated disc for being history’s all-time best-selling songwriter and recording artist. Guinness has also noted items such as the world’s “Most Expensive Pen” or “Most Expensive Board Game” as containing rhodium.