Gather a selection of magnetic and non-magnetic rocks. Split your class into small groups and hand out an equal number of both to each group. Walk the class through the basics of magnetic attraction and then give each group a selection of items that respond to magnetic forces. Vary the size of the objects so students can see which types of magnetic rocks possess the greatest potential for moving or pulling metal.
Magnetism is a property that can be transferred to other materials. When you rub a magnetic rock against a paperclip, for example, the paperclip will remain magnetic for a short period of time. Distribute a variety of objects to your class along with one magnetic rock per group. Ask the class to use the rocks to determine which materials are most receptive to transferred magnetism and which ones hold their magnetic charge the longest.
Explain to your students that the Earth itself generates a massive magnetic field. It is this field that causes a compass to point north – without this magnetism navigation by compass would be impossible. Distribute various magnetic rocks to your class and ask them to determine which rocks have the greatest potential to interfere with the performance of a compass. You can then apply this information to the geographic areas from which the rocks originated, drawing assumptions about navigational problems in the area.
Magnetism is a powerful force but only at very short ranges. This is what allows a massive junkyard magnet to pick up a car without dumping over a scrap heap a few feet away. You can teach your students about this basic principle of magnetism with a few rulers and some magnetic rocks. Ask your students to place one rock at the end of a ruler. They can then drop a paperclip at a certain distance from the rock. By varying the distance at which each paperclip is dropped, students can deduce which magnetic rock has the longest range.
All rocks have some sort of magnetic potential, so the field is wide open when it comes to gathering magnetic supplies. Try testing rocks like lodestone, magnetite, limonite and haematite, as well as more common rock types such as granite, limestone and shale. Different rocks will demonstrate easily noticeable differences when exposed to magnets and magnetic metals. If possible, ask students to bring rocks from home to test the magnetism of rocks that are natural to your area.