Program aims to educate young consumers about mined stones’ positive qualities.
Pieces sell for $310,100 against $231,400 upper price at Hong Kong auction.
Piece will carry $2.6 million high estimate at September 19 sale.
Unmounted stone was top seller, raking in $5.8 million.
Several big-ticket items did not appear in results.
Lot becomes second-most valuable jewel ever sold at auction.