The same can be said of bismuth, which has a mass abundance half less than that of palladium, but with a price of only a little more than a tenth of tellurium's price. In terms of mass abundance, expressed in parts per billion (ppb), here's how the nine precious metals are ranked (rare to rarest): 9th: silver (75 ppb); 8th: palladium (15 ppb); 7th: gold (4 ppb); 6th: osmium (1.5 ppb); 5th to 3rd: iridium, rhodium, and ruthenium (1 ppb); 2nd: rhenium (0.7 ppb); and 1st: platinum (0.003 ppb). Ruthenium - Karl Karlovich Klaus, a Russian chemist and naturalist, is usually credited with the discovery of ruthenium (in 1844). He discovered it from platinum ore samples he obtained from the Ural Mountains in Russia. He named this precious metal after "ruthenia", the Latin word for Klaus's home country Russia. Small quantities of this element also occur in pentlandite (an iron-nickel sulfide) obtained from Sudbury in Ontario, Canada, and in South Africa's pyroxenite (an ultrabasic igneous rock) deposits. Commercially, ruthenium is obtained as a by-product from copper and nickel processing (as how all the other platinum group metals are obtained), although it is likewise obtainable through direct processing of platinoid ores. Ruthenium tetroxide, a yellow, diamagnetic tetrahedral ruthenium compound, is highly toxic and volatile; it may explode if it comes into contact with combustible materials. Osmium: Osmium, like iridium, can ignite spontaneously in air when in finely divided form. The compound osmium tetroxide, in particular, is highly volatile and is extremely toxic if accidentally inhaled, ingested, or comes into contact with the skin. mol-1 Atomic: Oxidation States: -3, -1, 0, 1, 2, 3, 4, 5, 6 Electronegativity: 2.20 (Pauling scale) Atomic Radius: 136 picometre Covalent Radius: 141 6 picometre Because of its characteristic of being very brittle, pure iridium is quite difficult - almost impossible, in fact - to machine. Its primary use is as a hardening agent for platinum. While gold's price is determined through trading in the derivatives and gold markets, its daily benchmark price is provided in a procedure called the London Gold Fix. In this procedure, the price of the precious metal is determined each business day on the London market. The fixing is done twice - once in the morning and another in the afternoon.