Program aims to educate young consumers about mined stones’ positive qualities.
25-carat yellow-diamond ring by Bulgari achieves $2.8 million.
17.61-carat stone is largest internally flawless gem of its color ever to appear at auction.
Auction house will not sell last 300 pieces due to backlash over collection owner’s Nazi ties.
Auction house hires Tom Burstein as department’s director, and Peggy Gottlieb as senior specialist.
London exhibition will run from September 4 to 10.
Kashmir sapphire weighing 7.58 carats fetches $1 million — more than double its upper estimate.
Leslie Roskind served at Christie’s for 17 years.
Necklace estimated to sell for up to $500,000.
4.83-carat, blue diamond ring is top seller, bringing in $8.8 million.
Cushion-cut stone carries high estimate of nearly $435,000.