Size: 11.5 cm Origin: Inner Mongolia, China

Size: 11.3 cm Origin: Inner Mongolia, China

Optical calcite with birefringence, as used by Vikings as a compass Size: 4.7 cm

Optical calcite with birefringence, as used by the Vikings as a compass Size: 4.3 cm...

Optical calcite with birefringence, as used by the Vikings as a compass Size: 3.8 cm...

Optical calcite with birefringence, as used by the Vikings as a compass Size: 5.7 cm...

Optical calcite with birefringence, as used by Vikings as a compass Size: 4.4 cm

Size: 4-6 cm

Size: 9.7x6.7x4.5 cm