It's also 99.999% pure! From Wikipedia:
On May 3, 2007, the Royal Canadian Mint unveiled a Gold Maple Leaf coin with a face value of One Million Dollars,[1] though the gold content was worth over $2 million at the time. It measures 50 cm in diameter by 3 cm thick and weighs 100 kilograms, with a purity of 99.999%. The artist is Stanley Witten. The coin is mainly a promotional product to give the mint a higher international profile.[1] The 100-kilogram coin was conceived as a one-off showpiece to promote the mint's new line of 99.999 per cent pure one ounce Gold Maple Leaf bullion coins[1] but after several interested buyers came forward the mint announced it would manufacture them as ordered and sell them for between $2.5 million and $3 million. As of May 3 2007 there were five confirmed orders.