Christie's will be auctioning two of the world's most exceptional jewels in its April 22 sale.

The Emperor Maximilian Diamond, a 39.55-carat colourless stone, will sell alongside The Catherine the Great Emerald and Diamond Brooch.

The latter features a Colombian emerald weighing over 60 carats.

The Emperor Maximilian Diamond and the Catherine the Great Emerald and
Diamond Brooch

The rare diamonds are estimated to sell between $1m and $1.5m, and boast a truly exceptional history and provenance.

Both the diamonds will be previewed at Christie's Hong Kong today and tomorrow (April 8-9) before the winning bidder is revealed on April 22 in New York.

Meanwhile, Sotheby's Australia's upcoming April 12 sale of antique and contemporary jewellery boasts the first-ever red diamond offered for public auction in Oz.

The Argyle diamond: the first red diamond to auction in Australia

Carrying a pre-sale estimate of $645,065 and $921,556, the 0.82-carat, fancy purplish-red Argyle diamond flanked by a pair of fancy blue diamonds in a round brilliant-cut diamond surround.

The above is set into a platinum ring. It will sell with a letter from Argyle Diamonds confirming its rarity.

All prices are shown in US dollars.