Definition of "aquamarine"

Before we could embark on the details of his mother's health we were joined by a fair, plump woman of indefinite age, who had once been—and at moments still was—very pretty. She wore a simple black silk dress, perhaps in deference to Tilly's death, though the note of mourning was jarred by flamboyant aquamarine ear-rings and too much rouge.

1956, Delano Ames, chapter 4, in Crime out of Mind‎