The diamonds to be sold include Diavik Helios, a 74.48 ct Fancy yellow diamond, which was recovered from the Diavik diamond mine in Canada.
"Since the Diavik mine began production in 2003 it has produced on average only five large yellow diamonds each year, in effect less than 0.001% of Diavik's annual production," said Rio Tinto general manager of sales and marketing for the diamond division, Patrick Coppens.
"The Diavik Helios is an exceptional diamond in terms of its colour saturation and clarity and will be in strong demand from coloured diamond specialists around the world."
The company will auction 28 399 carats of rough diamonds from the Australian mine, including a 26-carat white gem-quality rough Argyle diamond.
"Since it began production in 1983, the Argyle mine has produced more than 865-million carats of rough diamonds," said Argyle mine general manager Andrew Wilson.
"With the mine closing at the end of 2020 the Argyle rough diamonds presented at this tender are a final rare and collectible offering from one of the world's greatest diamond mines."
Mathew Nyaungwa, Editor in Chief of the African Bureau, Rough&Polished