Larimar is a type of pectolite, and pectolite is found all over the world, but only in the Dominican Republic is this volcanic blue found. It is caused by the addition of copper (rather than calcium) at its formation.
Obviously it has been known for centuries by native tribes, and an attempt to mine it by a priest in 1916 was rejected, so it was not "discovered" until 1974 washed down the Bahoruco river into the turquoise Caribbean waters.
What is amazing - yet again - is how larimar, mined deep underground inland, looks so precisely like the transparent turquoise waters on the Caribbean coast.
How indeed can hard, solid rock look so much like water?