There are some interesting articles on the iridescence:
https://www.gia.edu/doc/WN06A4.pdf
https://www.jstage.jst.go.jp/article/jmps/112/2/112_161114a/_article
The material was collected between September 2004 and August 2005.
A very similar (5 cm) specimen sold for S $1,358.00 on eBay, February 15th 2018!