Because of low circulation of palladium coins, palladium as an investment commodity is not as good as either silver or gold. Another reason for this is the relatively wider spread between the metal's buying and selling prices. Palladium is traded on the London Stock Exchange as an exchange-traded fund (ETF), under the ticker symbol LSE: PHPD. It was identified from the residue of platinum ore which was dissolved in nitro-hydrochloric acid (also known as aqua regia). Platinum ores are still the main sources today of iridium. The precious metal is likewise obtained as a by-product of mining nickel. Below are some of the properties of iridium. On the reverse of the coin is an image of the springbok, an antelope specie which is a South African national symbol. Atop the image is an inscription of the name of the coin, in capital letters, while below it is the coin's gold content, inscribed in Afrikaans and English. Special samples of the coin (proof Krugerrand) are minted and offered as collector's items. Its other physical characteristics include its being malleable, ductile, and dense. But while platinum is generally resistant to corrosion, it is corroded by certain elements, such as cyanides (potassium cyanide or sodium cyanide), caustic alkalis, sulfur, and any of the five halogens (astatine, bromine, chlorine, fluorine, and iodine). 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). coin (FV: CD2), were issued by RCM, but only in 1994. In 2009, the 1 oz. coin was reintroduced. All coins, which have legal tender status in Canada, consist of 0.9995 pure platinum. The Australian Platinum Koala: The Australian Platinum Koala bullion coins were first released in 1988 by the Perth Mint, the oldest currently operating mint in Australia.