This is a few small examples of the rock known as chert. It is a sedimentary rock, and sometimes contains small fossils, as shown in the sample on the left.
Photo by Lucy Gridley
The description states:
CHERT
Banded and mottled Chert (embedded fossils). Usually occur with limestone or dolomites, and found throughout Michigan in glacial drift. Chemically the same as Japer and Flint. Can be tumbled or cut for lapidary work.
–As it has properties similar to flint, it was also used in making bladed implements and weapons. The card is dated 1962.