The Australian five ounces gold piece (abbreviated as 5 oz and designated with Au for "gold") is a bullion coin format. Uniquely, in Australia there are two mints authorised to strike legal tender: the Royal Australian Mint (which also makes the country's circulating coinage) and the Perth Mint which only makes collector and bullion coins, as well as other bullion products.
Both mints endeavour to create coins with attractive designs, and to introduce new designs and themes often, in order to raise the numismatic value of the coins over the value of previous metal used.
The Mint says about this coin:
Superbly crafted by The Perth Mint from 5oz of 91.67% rose gold in proof quality, this stunning creation pays tribute to north-western Australia's Kimberley region and incorporates an authentic, handset Argyle pink diamond.
In far north-western Australia lies the pristine wilderness known as the Kimberley. This vast outback region encompasses ancient gorges and waterfalls, incredible rock formations, white sandy beaches, and an abundance of nature including iconic bottle-shaped boab trees. Famous for its spectacular sunsets which ignite the evening sky with vivid colour, it is also the source of the world’s most famous pink diamonds, sought-after worldwide by collectors and connoisseurs for their extraordinary beauty and rarity. | 
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