(IDEX Online) - A Japanese collector paid $15.7m for a 102-carat, D-color, flawless diamond - a record high price for a gem in an online auction.But it was nowhere near as much as experts had predicted. Before Monday's sale by Sotheby's Hong Kong, there was speculation that the exceptionally rare diamond, offered without reserve, could fetch over $30m.Nevertheless, it smashed the previous record for an online diamond sold at auction - $2.1m at Christie's for a 28.86-carat diamond in July.The 102.39-ct Type IIa stone was only the eighth D-color diamond +100 carats ever to have been offered at auction. The sale price works out at $153,285 per carat. Sotheby's didn't name the buyer but revealed that he bid over the phone and had named the stone Maiko Star after his second daughter. Last year the same buyer named an 88.22-carat diamond Manami Star after his eldest daughter.Patti Wong, chairman of Sotheby's Asia, said: "This extraordinary gem needed no help from a pre-sale estimate or reserve to reach its rightful price - just the instinctive desire of collectors to own one of the earth's greatest treasures."The stone, described as "the size of a lollipop", was cut by Diacore from a 271-carat rough diamond at the Victor Mine owned by De Beers in Ontario, Canada, in 2018. It was the second-largest oval diamond of its kind ever to be sold at auction.