The 24th annual Rio Tinto Argyle Pink Diamond Tender, called the world’s most exclusive diamond sale, is being held in major cities around the world.

The first tender was held in Perth. Sales will be held in New York, London, Hong Kong, and Tokyo during the month of September and in Sydney in October.

The tender will feature 65 of the world’s rarest pink diamonds from the Argyle mine in Australia. With Argyle mine supply currently predicted to run out by 2018, the rarity and exclusivity of these treasures has enhanced their image as both a key investment option and a must-have.

This year’s tender is featuring, for the first time in seven years, a heart shaped pink diamond. There are also a number of purplish reds, intense and vivid pinks and three rare violets that add to this collection. In total this collection showcases 62.46 carats of diamonds with 30 diamonds more than one carat in size.

This year, for the first time, Rio Tinto has bestowed names on what it considers to be the two “hero” stones from the collection. Aphrodite, a 1.01-ct. round purplish red takes its name from the Greek Goddess of Love and Passion whilst Ocean Seer, a 1.41 rare violet stone, symbolizes ancient wisdom and serenity.

Since the first pink diamonds were recovered from the mine in 1985, demand for these exceptional gems has attracted a coterie of elite and discrete buyers including royalty, heads of state, celebrities and other very wealthy individuals.

“This is nature at its very best. The rarity of these gems and their intense color and energy, continues to excite passions among all who see them,” said Raj Kandiah, general manager Argyle Pink Diamonds. “Rio Tinto’s commitment to this unique product has been demonstrated in the development of an underground mine at Argyle and continued investment in its dedicated, state-of-the-art cutting and polishing factory in Perth.”

The pink diamond jewelry market has grown in popularity and is now worth hundreds of millions of dollars as the desire to own the rarest has sent prices skyrocketing. Pink diamonds are worth approximately 20 times the cost of the same size white diamond. However, the sky is the limit when it comes to Rio Tinto’s Argyle Signature Stones— each diamond is so unique that it warrants an individual price tag.

Despite demand, attendance to the Pink Diamond Tender is restricted to around one hundred key clientele from around the world who will personally view the diamonds in a secret location in Sydney, Tokyo, London, Hong Kong, New York, or Perth. Due to the high security required for the Tender, the exact location is not revealed to bidders until the very last minute. Bids are confidential and the names of successful bidders and the values achieved are not disclosed. Those that are successful will be notified personally in October.

JCK