Magnetic Rocks: Lodestones

Lodestones are naturally occurring magnetic rocks. These iron-bearing rocks became magnetized by their positions in Earth's crust in relation to its magnetic field. Lodestones have both north and south poles. For this reason, these rocks were used in the first compasses. In this activity you will see how to magnetize a rock that contains iron so it becomes a lodestone.

Materials

Iron-bearing rock (such as magnetite or hematite); Iron filings (about 1 tbsp); Sheet of paper; Strong bar magnet

Activity

1. Hold the rock to be magnetized in your left hand. Sprinkle the iron filings on top of the rock. Quickly turn the rock over to allow the filings to fall onto a piece of white paper. Note whether any of the iron filings stick to the rock.
2. Remove the filings from your desktop.
3. Hold the bar magnet in your right hand and stroke the stone gently with one pole of the bar magnet. Do this 75 to 100 times. Then put away the bar magnet.
4. Hold the rock in your left hand and place the teaspoon of iron filings on the side of the rock you were stroking with the magnet.
5. Turn the rock upside down above the white paper. Examine the rock to see whether any iron filings stayed attached.

Follow-Up Questions

1. Did any iron filings stay attached to the rock when you flipped it over before you stroked it with the magnet?
2. Did any iron filings stay attached to the rock when you flipped it over after you stroked it with the magnet?
3. Could you now use this rock to make a magnet? Explain.

Answers

1. No.
2. Yes.
3. Yes. The rock that was temporarily magnetized can also magnetize another magnet.

Extension

Repeat the above activity, but test different types of rock. Test other iron-bearing rocks such as limonite, siderite, and taconite. Also test rocks that do not contain iron. Determine whether all types of rocks can be magnetized.