Sedimentary rock samples, of approximately the same size. Carolina Biological sells packs of 10. You will only need 3 samples from each pack.
Limestone (3 samples)
Sandstone (3 samples)
Optional: Magnifying glass
You will also need to gather these items:
Paper plates (3)
Optional: Camera
Eyedropper
Mineral oil; available at drug stores
Clock
Lab notebook