The Australian Trilogy is comprised of three one-kilogram coins struck from gold, platinum and rose gold, with each featuring a different native animal.

Each of them has either a pink, purple-pink or violet diamond, which were unearthed at Rio Tinto’s (ASX:RIO) Argyle mine in the east Kimberley region of Western Australia.

One of the coins, made 99.99% of gold, portrays two kookaburras on a wooden fence looking at a 0.47-carat round brilliant cut fancy deep purple-pink diamond.

The kangaroo coin, crafted from 99.95% pure platinum, depicts the marsupial in an outback plain with a 0.46-carat emerald-cut fancy dark grey-violet diamond.

And the 91.7% rose gold koala coin depicts the animal beneath a eucalyptus tree beside a 0.58-carat emerald-cut fancy intense pink diamond.

The Perth Mint will only ever release one of The Australian Trilogy 2017 Collection, Rio Tinto said in a statement.

The company’s Argyle mine generates more than 90% of the world's pink diamonds, yet less than 0.1% of all the rocks found there are pink.

The 2016 Kimberley Treasure coin, valued at $1 million, sold to an international buyer within 48 hours.