A simple millstone
 |
A pestle and mortar |
Experiment
Testing
the hardness of stone
Take some seeds - wheat is best but any seeds
will do and try grinding them up in a
mortar. Use a pestle made of a
variety of materials e.g. wood, metal, stone, plastic.
Make a table to record which material is best to use for
grinding e.g:
| Material | course | medium | fine |
| wood | |||
| plastic | |||
| stone |