Origin and Composition

Origin and Composition

Summary of the article that appeared in the Listín Diario Supplement, March 29, 1986

By Rafael Osiris de Leon

About 100 million years ago, when our island was just an elongated rock mass emerging from the ocean floor, basic volcanic rocks, mainly andesites and basalts with a porphyritic texture, were placed at the eastern end of what is now the Sierra de Bahoruco .

These rocks, at first, were incandescent solutions that crystallized as the passage of time allowed their temperature to drop.

The mineralogical composition of those solutions was very varied, predominating the Silicon-Oxygen association ( Silicates ) in different forms and states that were mixed with aluminum, sodium, calcium, ferric, magnetic elements, etc., to form both essential minerals and minerals. accessory minerals of those rocks in the process of crystallization. One of these mixtures, perhaps the least usual in that environment of chemical complexity and temperature drop, is that of Silicon – Oxygen with Sodic – Calcium elements in the necessary proportions to form small compact concretions of a bluish green color, fibrous appearance and silky shine. that nowadays the descriptive mineralogy defines as Pectolite.

A long time has passed since then; The Earth has revolved around the Sun at least a hundred million times and different species have existed throughout this chronology. But in that time interval, new incandescent solutions were injected under pressure, causing the consequent alteration of the pre-existing rocks, while the excess calcium contained in the sea waters precipitated in the form of Carbonate that was deposited on the ocean floor, completely covering the andesites and basalts, previously emplaced.

But the magmatic injections continued and forced these volcanic rocks to make their way upwards through the limestones, while the extensive massif of Bahoruco rose slowly and steadily.

Already by the end of the Miocene, these rocks were superficially exposed, so the sun, rain and wind began to take advantage of the structural weakness introduced by the alteration process, eroding it significantly.

This erosion process allowed fragments of volcanic rocks to move along the Bahoruco riverbed, including some with bluish-green inlays that, although exclusive to that region, went unnoticed from the times of Enriquillo until the beginning of this century. , when Father Miguel Domingo Fuertes , in a communication dated November 22, 1916, informed Archbishop Nouel about the presence of this pectolite.

Later, in 1974, Mr. Miguel Méndez , dedicated for years to the craftsmanship of semiprecious stones, and Mr. Norman Rilling , from the Peace Corps, collected some samples, which they tested in a craft workshop with very satisfactory results, deciding then to give to this mineral the name of LARIMAR. Some samples were later sent to the Smithsonian Institution, an institution that carried out tests for the corresponding mineralogical classification.