It's called Bear Canyon black and white fortification agate because the shape of the agate's concentric black and white bands resembles the footprint of a medieval fortress. In contrast, the more ...

The Fairburn, which is also the state gemstone, is what scientists call a fortification agate.

24. Pebble of ‘fortification’ agate. The ground plan of the ‘fortress’ can be seen on the polished side Toby KeelAugust 31, 2018 ...

An almost two-kilometer fortification has been constructed outside the Russian-occupied town of Hirske, in eastern Ukraine, new satellite images from Maxar Technologies show.

Two fortification agate samples. They are oval in shape with approximately 50-mm-long major axes and are characterized by a colorful and b bluish banding layers, respectively.