Reversible Twinning In Neodymium Pentaphosphate

For practising gemologists only. Neodymium pentaphosphate is a rare experimental synthetic material that shows reversible lamellar twinning under polarized light when gentle pressure is applied perpendicular to twinning planes. Take a look.

Useful link:
https://www.gia.edu/gems-gemology/spring-2020-microworld-reversible-twinning-ndp