Everything You Always Wanted to Know About Amber
The fossil resin of the Dominican Republic is believed to have been encountered already by Columbus during his second expedition to the West Indies in the years 1494–1496. Minor mentions, which only appeared 400 years later, reportedan amber-bearing formation (the Monte Cristi mountain range) and inclusionsfound in the amber.
In the 1960s, great interest, especially among palaeoentomologists, was generated by the fossil resin of the Dominican Republic due to the great number of clearly visible arthropod inclusions found in it. The inclusions are not surroundedby the halos of frothed amber. The value of the pieces with an abundance of organic remains was additionally increased by the Santo Domingo government when it issued a 1987 decree to forbid the export of inclusions without the permissionof the National Natural History Museum.
The composition of the arthropod fauna preserved in Dominican amber is significantly different from the associations found in Baltic amber. This is related to the climate and considerable isolation of the islands of the Caribbean. Interestingly, there are specimens of Dominican amber in which a very large number of individuals were embedded at the same time, up to 200 in one piece. Amphibians and reptiles— iguanas and geckos— can also be found in it. More than 10 lizards and a frog have already been found. Bird feathers are also found in greater numbers than in Baltic amber.
Next to animal inclusions, the fossil resins of Central America have impressiveplant inclusions. The results of botanical tests and Infrared Spectroscopy ofcontemporary resins, Chiapas amber and Dominican amber made it possible toindicate the parent trees of these resins in the 1960s. They were broadleaf trees, compared to the contemporary species of the genus Hymenea, of the leguminousgroup (family Leguminosae). For Chiapas amber, the species of Hymenea courbaril L. was indicated among the contemporary Leguminosae; it grows alongsides treams and does not generate much resin. For Dominican amber, George Poinar has indicated the now extinct species of Hymenea protera.
Today, amber is mined in the Dominican Republic using a primitive method of digging small shafts, or side drifts, on mountainsides. The deposits are quite abundant, with amber found in Palaeogene sandstone or greasy clay. The most
numerous finds come from the Northern Cordillera, between Puerto Plata and Santiago. In Palo Kuemado, where amber finds have been recorded for 50 years, there are three mines with significant output. The largest mine is located in Palo Alto: on an area of ca. 5 km2, there are many “one-man” headings. In this area, out of 100 kg of output, one can sometimes get 30–40 kg of specimens with inclusions; it is also here that the largest piece of mass 13 kg was found, plus some smaller ones of 7–9 kg. According to recent estimates, 2–5 tonnes of amber are excavated here. The age of this mine’s sediments has been dated to Oligocene– Lower Miocene. Amber is found in fine-grained, compact, grey-blue sandstone with mica and coal inclusions.
Dominican amber comes mainly in transparent varieties: from light yellow to cognac-coloured, sometimes red. The varieties with strong fluorescence are very frequent and especially sought after. Over a month, ca. 10 kg of rare blue amber is obtained, out of which 25% of the best sort remains after purification. The blue, or even rarer greenish, colour is visible in reflected light or on a dark background. The blue variety is harder than the remaining ones; sometimes disc-shaped pieces are found. This variety does not contain organic inclusions, and if there are any, they seem somewhat squashed. All this suggests that the resin has undergone heavy diagenetic changes. Growth rings in Dominican amber can sometimes be hairline-thin and do not alter the amber’s transparency. This may be an indication of a lower viscosity of the resin than in the case of Baltic amber.
Europe’s largest collection of Dominican amber is kept at the Museum am Löwentor in Stuttgart, Germany.
Dominican amber competes with Baltic amber on the European market. However, its very good polish quite quickly develops superficial cracks. Thermal processing has not been applied to Dominican amber as yet; it is left the way nature has made it.