The unmounted, 12.20-carat, G-color, SI1-clarity diamond came from the descendants of Irene Langhorne Gibson, who is thought to have modeled for husband and illustrator Charles Dana Gibson. The famed American artist created the Gibson Girl image, a personification of the feminine ideal that became popular in the late 19th and early 20th centuries.

Irene Gibson Emery, the daughter of Irene and Charles, received the stone from John Josiah Emery on their engagement in 1926, Skinner said Wednesday. The US auction house expects to sell it for $100,000 to $150,000 at its Important Jewelry sale on May 18 in Boston, Massachusetts.

Other jewelry from the family will also be up for sale, as will pieces from noted art collectors Daphne Farago and Lois Torf.