When is a Rock Like a Magnet?

When is a Rock Like a Magnet?

Author: Sid Parkins
Date: September 28, 2012
 http://www.sciencenewsforkids.org/2012/09/making-rocks-into-magnets/
When it's a lodestone? New research by geologist Charles Aubourg and his colleagues at the University of Pau shows that, when heated, certain types of rocks can actually become natural magnets. The strongest and most common is the lodestone. This is because lodestone is made-up of a mineral called magnetite, which creates a persistent magnetic field. The rocks Aubourg and his team used when experimenting also contained small amounts of an iron-bearing mineral called pyrite. The experiment was a long process which included heating a rock inside a strong magnetic field for 25 days at 50 degrees Celsius, 25 days at 70 degrees, 25 days at 80 degrees, 10 days at 120 degrees, and another 10 days at 130 degrees.