There are many common materials that are not attracted to magnets, water, wood, animals, plants... etc., however some of these non-magnetic materials actually repel magnetism.

Materials that repel magnetism are called diamagnetic, graphite and bismuth having the strongest effect.

The following page by Martin Simmons (UCLA) gives a good primer about diamagnetic levitation; Diamagnetic Levitation
For a more indepth and scientific understanding, Martin's paper in pdf format;
Magnetic Levitation at your fingertips, gives equations and examples for magnetic levitation.

Reade Magnetic properties & susceptibilities chart gives a useful insight into the magnetic properties of different materials.

Cool experiments with diamagnetic materials and NdFeb mangets.
Fun with Diamagnetic Levitation

GerAx have some more good info;
GerAx - Diamagnetic levitation., check out their experiments, and levitation jig.

For some commercial applications of diamagnetic levitation, see;
Aussie Magnets' design portfoloi, the floating, working lightbulb is amazing!

After looking around at commercially available levitation jigs and materials, I thought Lego, being non-magnetic, would make a very good construction material for my jig.

I also found a supplier of bismuth - in shot form, a non-toxic replacement for lead shot in shotgun cartridges. The bismuth shot does contain some tin, however the shot is much cheaper than pure bismuth (158 per kg from one source!) and works adequately.
I puchased a 3kg jug of shot, although your local dealer may split cartridges for smaller amounts.

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