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 at its formation.
Obviously it has been known about for millennia by native tribes, and an attempt to mine it by a priest in 1916 was refused, so it was not 'discovered' until 1974 when it 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?