Growing crystals is a simple project for homeschooling families or to alleviate summer boredom. There are commercially available crystal making kits available, but most revolve around a simple spice found at most well-stocked grocery stores. Save money and make your own crystals with your children instead.
This is bismuth, a brittle metal with an iridescent oxide tarnish that produces rainbow colours. It's the most naturally diamagnetic metal in the world, which means it can create a magnetic field in opposition to an externally applied magnetic field.