'Flawless' white diamond could fetch over $33m

London - A white diamond billed as the largest and purest of its type to come to market is expected to sell for well over $33m. 

Sotheby's auction house says the 102.34-carat gem mined in Botswana "is the only known round brilliant-cut diamond over 100 carats perfect according to every critical criterion" — carats, colour, clarity and cut.

Sotheby's diamond department head Patti Wong called it "over 100 carats of flawless perfection".

The diamond went on display on Thursday at Sotheby's London showroom and is being offered for private sale. It's expected to fetch a price "considerably higher" than the $33.7m auction record for a white diamond.

The auction record for any diamond is held by the "Pink Star", which sold for $71m at Sotheby's Hong Kong in 2017.