Face Blindness and Stones.

Cecilia Burman has prosopagnosia, commonly known as “face-blindness.” She wrote Face Blindness and Stones to illustrate what this condition is like, comparing her difficulty in facial recognition to the way a normal person would have trouble telling one stone from another, and some of the coping mechanisms she uses. http://www.prosopagnosia.com/main/stones/index.asp -via Reddit