Quiz on a Friday?! That takes me back to high school; I always had quizzes on Fridays. Thursday nights were never relaxing. But, you are not being graded on this. Take a guess.
What is this architectural material?
What can you tell me about? Where is it found? How old is it? What brought you to this conclusion?
(Yes, I will post the answer.)
EDIT: A better photograph.
Scale: roughly 3"x6".
Preservation in Pink 