After five years Rio Tinto’s (LON:RIO) multi-million-dollar Argyle pink diamonds are back in Japan, where the company will be showcasing the world's rarest red, pink and blue gems until Oct. 2.

Included in the Tokyo preview are three Fancy Red diamonds, representing the pinnacle of value and ultimate rarity in the diamond industry. The hero of the collection is a 1.56 carat round gem, the Argyle Phoenix, named in honour of the newly commissioned Argyle underground mine.

Prices will not be known until the tender closes, but based on the recent price of $1.6 million per carat for a red diamond set at auction, Argyle Phoenix could fetch over $2.5m.

"We are delighted to be back in Tokyo … The Japanese market is very important to us and over the past 20 years has shown, and continues to show, an unerring demand for Argyle pink diamonds," said in a statement Argyle Pink Diamonds manager, Josephine Johnson.

In the last two decades, Japan has consistently shown a strong interest for Argyle pinks, and it remains the largest market for those stones, especially the lighter shades of pink.

According to Rio, Japan is also a market that covets heart shaped diamonds, and the matching pink and blue heart shaped diamonds in the 2013 Tender collection are likely to be strongly contested.