A white diamond the size of a small egg has sold for $30.6 million at a Hong Kong auction, although a blue diamond that was the night’s other highlight with a $19 million estimate failed to sell.

Two phone bidders competed for the 118-carat white diamond from Africa in six minutes of measured bidding until one dropped out in the Sotheby’s jewellery auction, part of autumn sales of art and collectibles by the firm and its rivals.

The twice-yearly ritual in Hong Kong draws wealthy collectors from mainland China and other Asian countries and has made the city one of the world’s busiest auction hubs.

A 7.6-carat blue diamond failed to reach its reserve price

The “flawless” white oval diamond went for more than the previous record of $26.7 million for a white diamond set in May at Christie’s in Geneva. The stone, which weighed 299 carats when it was found in the rough in 2011, is the largest and most significant such diamond graded by the Gemological Institute of America.

The auction’s other highlight, a 7.6-carat, flawless, round, vivid blue diamond, failed to reach its reserve price.

The two gems were among 330 lots of rare jewellery that fetched a total of $95 million.

The world record price for a jewel at auction was set in 2010, when London jeweller Laurence Graff paid $46 million for a “fancy, intense pink” diamond weighing 24.8 carats. That record could be blown away in November when Sotheby’s puts a pink 59.60-carat diamond on the block which is expected to fetch more than $60 million in Geneva.