This region is the only locality of a blue (copper) variety of pectolite called Larimar. The material, formed by hydrothermally altered volcanic rocks, was (re)discovered in 1974 and used as gem/ornamental stone.
Ref.:
- N. Jb. Miner., Mh., Jg. 1991, H.1, 14 - 22
- Lapis 21(1), 1996
- http://www.larimarmuseum.org/larimarinfo.html