Larimar is the trade name for a blue variety of pectolite, NaCa2Si3O8(OH), found in commercial quantities at a single locality in the world: the Los Chupaderos mine in the Bahoruco Mountains of the Barahona Province of the Dominican Republic. The trade name was coined in the 1970s by Miguel Mendez, the Dominican who is generally credited with the rediscovery of the deposit in 1974, and combines 'Larissa' (his daughter's name) with 'mar' (the Spanish word for sea, evoking the Caribbean blue colour of the stone). Larimar is one of only a small number of named gem materials with a single commercial source globally, and its production has remained essentially limited to the Dominican mine throughout its commercial history.

Mineralogy and physical properties

Larimar is a blue variety of pectolite, a mineral of the wollastonite group, typically found in colourless, white or grey colour in association with various basaltic and metamorphic rocks worldwide. The blue colour of larimar is unusual for pectolite and is attributed to the substitution of copper for calcium in the structure, with associated trace elements contributing to the colour variation. The hardness is approximately 4.5 to 5 on the Mohs scale (relatively soft for a gemstone, requiring care in setting and wear), the specific gravity is around 2.84 to 2.90, and the refractive index is in the range 1.59 to 1.65. The colour ranges from pale sky blue through medium blue to deep blue, often with white veining or patches of green, with the most prized material being a saturated medium blue with attractive marking.

Geological setting

The Los Chupaderos deposit is hosted in volcanic rock of the Cretaceous Sierra de Bahoruco volcanic complex. The pectolite occurs as nodules and vein fillings within altered basaltic volcanic rocks, formed by hydrothermal activity in the cooling and weathering of the volcanic complex. The mining site is in mountainous terrain at moderate elevation, accessed by a mining road from the coastal town of Barahona. Mining is principally underground, with shafts and adits driven into the mountain to follow the larimar-bearing zones. The deposit's geometry, the relatively small areal extent of productive ground, and the considerations of safety and access have constrained the scale of mining operations.

History of the deposit

Larimar was first reported by a local resident, Padre Miguel Domingo Fuertes Loren, in 1916, who applied unsuccessfully for permission to explore the deposit. The deposit was effectively forgotten until 1974, when Miguel Mendez and a local Peace Corps volunteer, Norman Rilling, found pieces of the blue stone on the beach and traced them to the source in the Bahoruco Mountains. Mendez registered claims and began commercial production, coining the name Larimar. From the late 1970s onward the material has been mined commercially and entered the international gem market, principally as cabochon material for jewellery and as ornamental and lapidary material for collectors.

Production and the trade

Mining at Los Chupaderos has historically been conducted by small operators working under various concession arrangements with the Dominican government and with the involvement of local cooperatives. Production has been irregular, with output strongly dependent on which zones of the deposit are being worked at any given time. Higher-grade material with strong saturated colour is in continuous short supply relative to demand, and prices for the best material have appreciated over the past two decades as the international jewellery market has incorporated larimar into Caribbean and tropical-themed lines. The Dominican government has periodically attempted to formalise mining and to establish quality controls; the trade convention is that larimar should be from this single source, and material from any other locality (occasional reports of similar blue pectolite occurrences from other countries) does not properly carry the trade name.

Identification and treatment

Larimar is identified gemmologically by its distinctive blue colour, its softness, its specific gravity, and its mineralogical character as pectolite. The colour is essentially never enhanced by treatment (in contrast to many other coloured stones), and the material is sold in its natural state. Some larimar is impregnated with wax or resin to stabilise softer or more porous material, and disclosure of any such treatment is required under CIBJO and FTC standards. The material is sensitive to ultraviolet light: prolonged exposure to direct sunlight can cause the blue colour to fade, and larimar jewellery is generally recommended for storage in protective conditions when not being worn.

Cutting and use

Larimar is cut almost exclusively as cabochon, freeform or shaped stones for jewellery setting, and as slabs for inlay and ornamental work. The relatively low hardness (4.5-5) and the fracture pattern of the material make faceted cutting impractical and inappropriate, and the cabochon presentation is well-suited to the layered colour and patterning that the material typically displays. Larimar jewellery is most often produced in silver, although gold settings are also encountered, with the Caribbean and Dominican-origin association giving the material a particular cultural resonance in jewellery from the region. Major Dominican jewellers and a number of international firms have produced larimar lines.

Position in the gem trade

Larimar occupies a defined position as a distinctive Caribbean-origin gem material with a single commercial source, a strong cultural and geographical association with the Dominican Republic, and an attractive blue colour at moderate price points. Its softness and ultraviolet sensitivity place limits on its use in pieces subject to heavy daily wear, but it is well-suited to occasional wear, statement jewellery, and pieces designed to evoke the Caribbean colour palette. For the contemporary jeweller and dealer, larimar is one of the few named gem materials with a clear single-source provenance, which gives it an unusual marketing advantage in the broader coloured-stone trade.