Why did Mrs. Asher take a piece of the fossil in the novel, A Tangle of Knots?

Mrs. Asher originally took the fossil piece because it was her last day as an archeologist. She wanted something to remember the experience by, so she took the fossil and used it as a hairpin. She held onto it because it reminded her of a time when she was Fair, and all of the things she got to experience because her fate wasn’t determined by her Talent.