The Chalk Emerald is a 37.82 carats (7.564 g) Colombian emerald.
The Chalk Emerald ring
The royal rulers of Baroda State, a princely state in India, once[when?] owned the emerald. It was the centerpiece of an emerald and diamond necklace worn by the Maharani Saheba, who passed it down to her son, the Maharajah Cooch Behar.
In the 20th century, the emerald was sold to Harry Winston and recut from its original weight of 38.40 carats (7.680 g) and set in a ring designed by Harry Winston, Inc., where it is surrounded by sixty pear-shaped diamonds, totalling approximately 15 carats (3.0 g). The ring was donated by Mr. and Mrs. O. Roy Chalk to the Smithsonian Natural History Museum in 1972 and is part of the Smithsonian's National Gem and Mineral Collection.