Iron oxide baked into Mesopotamian bricks confirms ancient magnetic field anomaly 

 About 3,000 years ago in ancient Mesopotamia, brickmakers imprinted the names of their kings into clay bricks. Now, an analysis of the metal grains in those bricks has confirmed a mysterious anomaly in Earth's magnetic field. 

https://cdn.mos.cms.futurecdn.net/UZFintsSXMKsiEyQi5iCKf.jpg

https://www.space.com/iron-oxide-mesopotamian-bricks-ancient-magnetic-field-anomaly