In March 1978, the Premier Mine yielded yet another remarkable diamond, a triangular-shaped cleavage of the finest colour, weighing 353.9 carats. Like an earlier stone found at the Premier, the 'Niarchos', this one too travelled right through the various stages of mining recovery only to emerge at the final one, the grease table in the recovery plant. A spokesman for De Beers stated that the stone had been mined at a depth of 457 metres (1500 feet), thus seemingly discounting any possible connection with the 'Cullinan' diamond, which had been found merely 1.8 metres (6 feet) below the surface.
For seasons of security the news of the finding of the diamond was not released for two months. After it had been disclosed, the Press lost no time in speculating about possible destinations for the eventual polished gem. Prince Rainier of Monaco was obliged to deny reports that he was planning to buy it as a wedding present for his daughter, Princess Caroline, who was shortly to be married; another European royal family was rumoured to be interested; finally Emperor Bokassa of the Central African Empire, who had already spent £20,000,000 on his coronation, was said to have made an offer for the stone. In the end the Johannesburg firm. Mouw Diamond Cutting Works, purchased it for around £2,500,000. The diamond was named after Mrs Rose Mouw, who was renowned for her prowess in marking diamonds, the first process in cutting a gem.
The cutting firm then contacted their American partner, William Goldberg, who promptly purchased a share in the stone. When he set eyes upon it, Mr Goldberg explained, 'A lot of people are going to be interested - this is an unusually exciting diamond.'
The cutting was carried out in South Africa and produced three gems which became known as members of the 'Premier Rose' family. The largest, which has retained the name 'Premier Rose', is a pear-shape weighing 137.02 carats, cut with 189 facets and measuring approximately 43.40 by 23.20 by 18.93mm (1.71 by 0.19 by 0.74 inches). It was submitted to the Gemological Institute of America for certification where it received a 'D' flawless rating, symbols for the finest qualities of colour and clarity. It was the largest stone of this calibre to have been certified by the GIA. The weight of the 'Premier Rose' makes it the second biggest diamond, surpassed only by 'Cullinan 1'. The 'Little Rose' is also a pear-shape and weighs 31.48 carats, while the 'Baby Rose' is a brilliant of 2.11 carats. The final yield of 48 per cent was a high figure to obtain from what had been considered a very difficult, awkwardly shaped piece of rough.
The William Goldberg Diamond Corporation of New York handled the sale of the gems. The 'Premier Rose' was sold in 1979 to an undisclosed buyer for about $10,000,000; the sale of the two smaller diamonds followed soon after.