Larimar (also lorimar) is a rare blue variety of pectolite found only in the Dominican Republic. Its colorations vary from white, light-blue, green-blue to deep blue. The deep blue variant is known as volcanic blue.

On 22 November 1916 Father Miguel Domingo Fuertes Loren of the Barahona Parish requested permission at the Dominican Republic's Ministry of Mining to explore and exploit the mine of a certain blue rock he had discovered. Since nobody knew what the priest was talking about the request fell through and the blue stone discovery was delayed.

It was not until 1974 when at the foot of the Bahoruco Range, the coastal province of Barahona, a flash of blue in the beach sand caught the attention of Miguel Méndez and Peace Corps volunteer Norman Rilling and they scooped down to rediscover larimar. Natives, who believed the stone came from the sea, called the gem Blue Stone. Miguel promptly took his young daughter’s name Larissa and the Spanish word for the sea (mar) and formed Larimar, by the colors of the water of the Caribbean Sea, where it was found. As it turns out, the few stones they found were alluvial sediment, washed into the sea by the Bahoruco River. An upstream search revealed the in situ outcrops in the range and before long the Los Chupaderos mine tapped the only known larimar outcropping in the world.

Geologically speaking, larimar is a variety of pectolite, or a rock composed largely of pectolite, an acid silicate hydrate of calcium and sodium. Although pectolite is found in many locations, none have the unique volcanic blue coloration of larimar. This blue color, distinct from that of other pectolites, is the result of cobalt substitution for calcium.

Miocene volcanic rocks, andesites and basalts, erupted within the limestones of the south coast of the island. These rocks contained cavities or vugs which were later filled with a variety of minerals including the blue pectolite. These pectolite cavity fillings are a secondary occurrence within the volcanic flows, dikes and plugs. When these rocks erode the pectolite fillings are carried downslope to end up in the alluvium and the beach gravels. The Bahoruco River carried the pectolite bearing sediments to the sea. The tumbling action along the streambed provided the natural polishing to the blue larimar which makes them stand out in contrast to the dark gravels of the streambed.

The most important outcrop of blue pectolite is located at Los Chupaderos, in the section of Los Checheses, about 10 kilometers southwest of the city of Barahona, in the south-western region of the Dominican Republic. It is basically a single mountainside now perforated with approximately 2000 vertical shafts, surrounded by rainforest vegetation and deposits of blue-colored mine tailings.

Larimar jewelry is available on practically every street corner and beach in the Dominican Republic. Most jewelry produced is set in silver, but high grade stones are often set in gold.

Quality grading is according to coloration: white is low quality, volcanic blue high quality. Most cheap jewelry ranges between white and light-blue. High quality jewelry utilizes stones between sky-blue and volcanic blue, often in combinations of both. Greenish colorations are also known but not well regarded, unless the green is intense. It should be noted that pectolites are photosensitive, which causes the larimar to lose its blue coloration over the years.

Name: Larimar.

Family: Pectolite.

Variety of: Pectolite, NaCa2Si3O8(OH), Sodium Calcium Silicate Hydroxide.

Composition: Hydrated sodium calcium silicate with manganese.

Origin: Dominican Republic.

Hardness: 4.5-5.

Color: varies between white, light blue, sky blue, green-blue, and deep blue (aka "volcanic blue")

Uses: ornamental stone and semi-precious stone.

Cleavage: perfect in two directions, but not seen in this compact form.

Crystal System: triclinic