While these assay methods are suited for finished goods (again because they are non-destructive), three other methods are more suited for raw precious metals: Titration: This assay method is one of the most widely used laboratory technique, which involves the analysis and determination of unknown concentration of a given reactant. So that while the chemical element tellurium is considered one of the rarest element in the Earth's crust (its mass abundance being the same as that of rhodium, iridium, and ruthenium), its estimated price is only less than 5 U.S. dollars per troy ounce, and, therefore, cannot be considered a precious metal. While bullion coins are issued as legal tender, with nominal values assigned to them on minting, such face values are far below the commodity value of the metals themselves. Here's an example: Most of the gold coins issued by national governments, particularly those with currency values of between 10 and 100 U. On the obverse of the Krugerrand is the face of Stephanus Jonannes Paulus Kruger, fifth president of the South African Republic (note the surname Kruger and the South African currency Rand were combined to give this precious metal coin its name). Also here are the Afrikaans and English versions of the name "South Africa", both inscribed in capital letters. Being rare and, therefore, very precious, platinum has been made synonymous to things that are considered "of the highest quality". We hear for instance of a platinum debit card holder enjoying a wide range of privileges; or of a platinum award being handed out to a music album that has sold over a million copies. Along with the five other precious metals in the platinum group, ruthenium is generally found in ores in North America, South America, and the Ural Mountains in 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.