By Robert E. Woodruff, Ph.D.
Article in Lapidary Journal, January 1986
(Artículo en la revista Lapidary Journal, Enero 1986. Vea aquí la versión en español)
Travel to exotic places is one of the advantages of being an entomologist. In search of parasites for biological control of a weevil pest introduced from the West Indies to Florida, I first went to the Dominican Republic in 1972. The trip would mark the beginning of a long-term study of the fossil insects in Dominican Republic amber.
As a hobbyist lapidary, I keep an eye out for interesting materials found in the locales I visit professionally. On one subsequent trip to the Dominican Republic in 1975, I was presented with an unidentified, beautiful blue stone by Professor Eugenio Marcano, the premier naturalist in that country and a well-versed geologist and paleontologist. The specimen was a great surprise to me, primarily because little lapidary material is found anywhere in the West Indies.
In my many trips to 15 of the islands, I have found no agate, only a few jaspers, some petrified wood and of course the amber. There are some beautiful archaeological pieces of jade, the source of which I believe is yet to be discovered in the Dominican Republic. I find it difficult to believe that it is all trade goods from Central America, as is often suggested.
The material that I was given was obviously stream tumbled. It had been obtained from the Bahoruco River, Barahona Province, in the southwestern part of the country. A small number of jewelry pieces using the material could be seen in the market in Santo Domingo at that time. I was fortunate to be in Washington, D.C. sometime later and took my specimens to the Smithsonian Institution for identification.
Pete Dunn, of the mineralogy department, kindly examined them and stated that he had seen specimens of the material earlier and identified it as pectolite. This information was passed on by me and others to those involved with the mineral in the Dominican Republic. Several shops there now display brochures describing the material as blue pectolite based on that information.
Within a short time the material had become the subject of many rumors and considerable commercial interest. Later it was the subject of inquiries to the Mail Bag column of Lapidary Journal.
Its discovery has not been documented, but it is rumored to have been found by a Peace Corps volunteer named Norman Rilling in 1974. The history of the stone takes many turns. It was originally named Travelina by Miguel Mendez of Santo Domingo. This name, however, soon gave way to the current Larimar, coined by combining the first of Mendez’s daughter’s name, Larissa, with “mar,” the Spanish for sea, whose color the stone resembles. Anyone who has seen the exquisite blue-green Caribbean waters off the Dominican Republic will concur that this is an appropriate and descriptive name.
Because all mineral rights in the Dominican Republic belong to the government, it was necessary to obtain a “concession” from the Ministry of mines in order to pursue any commercial venture. A corporation was formed for this purpose by Mendez and the owner of the property, a lawyer named Luis Augusto Gonzalez Vega. The corporation, however, was able to mine for only a short time, and neither of these gentlemen is currently involved in mining.
Amid Tropical Splendor
The mine is located about 10 kilometers north of the main road from Barahona to Bahoruco; the road lies three kilometers east of the latter. Known as the Camino Arroyo a Filipinas, or the road to Filipinas, the dirt and gravel road follows several steep hills and is normally not passable without four-wheel drive. In addition, it is only poorly marked.
Nevertheless, the scenery, once found, is spectacular! The road gradually climbs from sea level through tropical forests covered with orchids and bromeliads, more commonly known as air plants. Coffee, bananas, citrus, mangoes and breadfruit proliferate. Few houses are to be seen along the way, and these are mainly temporary thatched huts with banana-leaf roofs.
Replacement Mineral
In the piles of debris, I’ve found small pieces of olivine and quantities of carbonized wood among the basaltic rock. The deposit is clearly volcanic, and gas pockets are filled with various minerals, Larimar is the most abundant filler. It is found in several shades of blue and green – from translucent, similar to gem-grade chrysocolla, to dark variscite-like green. Narrow bands are scattered through the basalt matrix but are of little lapidary value.
Much of the best quality Larimar appears to fill pockets created by the volatization of trees, burned by volcanic activity. Naturally, this process was variable, and some trees were more rapidly and completely burned out than others. As a result, there are some pieces of carbon, some with partial Larimar replacement, and some with no suggestion of their organic origin. I believe that all cylindrical pieces are replacements of wood.
What is Larimar?
When I started this article, over two years ago, I fully expected to have concrete mineralogical data to include. Dr. Frederick H. Pough had become interested, and samples were submitted to zeolite (lava-related minerals) specialists for analysis. The results of these tests are not yet available. Larimar has been tentatively identified as pectolite, but there is doubt among several mineralogists about this determination.
Because the material is of volcanic origin, and it is often a replacement, great variability exists in the composition. Undoubtedly there is some pectolite, but chemical analysis indicates minimal amounts of sodium. Some needle growth, within the blue areas, has high aluminum content, suggesting natrolite. Much of the material is calcium silicate with occasional native copper flecks. Recent finds include “scenic” pieces with red plumes (iron) on a blue background and white “clouds”. Other samples contain pieces resembling thomsonites, some talc and several micro-minerals.
Hardness varies, but most dark blue material is from 5 to 7 on the Mohs scale. The color sometimes produces reticulate patterns of blue and white and there is often a pronounced silky chatoyance. Pectolite is often splintery in a literal sense: The long needles can be hazardous to a collector’s fingers. This is not true of Larimar, where the material is much more compact and therefore cuttable. X-ray diffraction is suggestive of pectolite, but with some unusual peaks.
Some chemical analysis has been performed with scanning X-ray probe analysis (through the kindness of Steve Speck). Analysis has shown a lack of sodium in dark blue Larimar and the presence of aluminum and sodium in natrolite-like crystals growing into the Larimar.
Though it has yet to be precisely identified, there is no doubt that Larimar, whatever it is mineralogically, is a captivating and valuable material to the lapidary.
Acknowledgements
I have had considerable help during many aspects of this study and wish to thank the following: Dr. Frank Blanchard, Jake Brodzinsky, Francisco Cuevas, Pete Dunn, Nelson Fulgencio, Luis Gonzalez, Dr. Francis Hueber, Eugenio Marcano, Heinz Meder, Miguel Mendez, Frank Moya-Pons, Ramon and Antonio Ortiz, Jose Ottenwalder, Vicente Peres, Dr. Frederick Pough, Steve Sloan, Steve Speck and Noel Valette. In addition, I wish to thank all the friendly people of the Dominican Republic who have assisted me during 12 trips there since 1973.
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