Gold As An Investment: Ways Of Investing In Gold Four of the nine known precious metals are regarded as investment commodities. Of these four, gold is the most popular. Investing in gold is a way of protecting against crises that may be brought about by economic or political instability or by social unrest. Here, the term "noble" serves as a modifying word, such that the electrical conductivity of materials is graded from noble to active. Using this definition for noble metals then, we will find that silver is less noble than, say, graphite (although graphite is an elemental form of carbon and, therefore, is not considered a metal). Trommel: This method involves the use of a screened cylinder to separate materials by size (trommel is Dutch word for "drum"). A trommel specifically consists of a rotating metal tube that is slightly tilted, with a screen at the discharge end. Attached to the inside part of the metal tube are lifter bars. The ranking appears different when the estimated world market prices, per troy ounce, of these nine precious metals are considered (estimates as of January 2010): 1st: Rhodium - USD2,750 2nd: Platinum - USD1,555 3rd: Gold - USD1,131 4th: Palladium - USD424 5th: Iridium - USD408 6th: Osmium - USD380 7th: Rhenium - USD194 8th: Ruthenium - USD173 9th: Silver - USD18 Of the nine precious metals, gold and silver are the best known. When alloyed with some of the other metals in the platinum group, such as iridium or platinum, osmium is used in certain applications where extreme hardness and durability are required. A couple examples of these are for electrical contacts and for tips of high quality fountain pens. Some of the properties osmium possesses are outlined below. When a small amount of ruthenium is added to titanium, the latter's corrosion resistance is improved significantly. As to its other applications, ruthenium is used in: 1. film chip resistors; 2. jewelry (when alloyed with gold); 3. high-temperature superalloys (used in making the turbine blades in jet engines); 4.