The Varieties of Baltic Amber

Dr Krystyna Leciejewicz

 The Museum of the Earth of the Polish Academy of Sciences (PAN), Amber Department

One of the properties of Baltic amber is the abundance of its varieties, with the enormous diversity of the amber’s degree of transparency and colour: from light yellow through various tints of yellow to white, bluish, greenish, beige and brown. This abundance of amber colours makes it a sought-after and valuable material in folk art and jewellery.

Primary varieties
 Based on internal structure, organic impurities and the degree of weathering, we divide succinite varieties into primary and secondary (Leciejewicz 2004, Leciejewicz, Kwiatkowska 2006, Leciejewicz, Mierzejewski 1983)
In the group of primary varieties the colour and degree of transparency is determined by the amber’s internal structure and organic impurities. The latest electron microscope research on the structure of amber shows that the number and the location of gas bubbles has a fundamental impact on the degree of the amber’s transparency and its colour. (Kosmowska-Ceranowicz 2006). Based on the degree of transparency we differentiate:
Transparent amber with a clearly layered structure. It contains either no gas bubbles at all or isolated, rather large bubbles 0.5-2.0 mm in diameter. The colour of transparent amber ranges from light yellow to dark yellow.
Translucent amber with certain fragments containing large clusters of gas bubbles which cause cloudiness. The amber’s colour is in a range of shades of yellow.
Opaque yellow amber has a solid structure. Certain concentrations of gas bubbles can sometimes occur on the nuggets’ edges. The amber’s colour covers an entire range of yellow and beige tints.
Opaque white amber where the number of gas bubbles can reach 900,000 per 1 mm2 and the internal structure is porous (permanent seed). The amber’s colour is white, sometimes bluish.
Earth amber with organic impurities and chips of wood makes up a group of primary varieties which are independent of their internal structure. Earth amber often contains numerous gas bubbles which appear during putrescing processes; animal and plant inclusions are also found. Earth amber can be brown to almost black and greenish in its transparent fragments.

In the Narew river basin, where the traditions of amber extraction and processing date back to the 15th century, a rich amber terminology developed to refer to the amber’s colour and degree of transparency, among other things. In The Pocket Dictionary of Polish Amber Varieties [Mały słownik odmian bursztynu polskiego] (1981), Adam Chętnik compiled 80 names of amber varieties, which apart from describing the colour and degree of transparency, also specify the amber’s degree of weathering, the type of the surface, place of origin, and even its suitability for processing and role in folk rituals.
 And so, in the transparent amber group A. Chętnik differentiates: trinket amber, which is completely transparent and light yellow, reddish glimmer amber, reminiscent of fire, honey-yellow honey amber, cloudy amber, in which turbid or opaque fragments form concentrations resembling clouds on a clear sky.
 In the translucent variety there is cloudlet and wooly amber, in which the turbidity causes streaks and concentrations reminiscent of small clouds or tufts of wool.
 In the opaque yellow variety we have: beige amber, cabbage-leaf amber, which has light yellow or whitish streaks against a yellow background, whose arrangement resembles the veins of a cabbage leaf, spotted amber, where fragments of various shades of yellow or white form clear spots, marble and mosaic amber, where multicolour fragments form arrangements resembling marble or mosaics, mixed amber, where there are a number of varieties in a single nugget. In ring amber and striped amber, fragments of various colours and degrees of transparency form stripes or arrangements resembling tree rings.
 The opaque white group includes: the chalk white chalk amber, bone amber, which is white with a shade of yellow resembling ivory, and the unique blue varieties. They contain so many gas bubbles that their interior seen under an electron microscope has the structure of permanent seed.
 The earth amber group of varieties with foreign substances of plant origin include: dappled amber, in which small grey or black pieces of plant detritus appear against a yellow or white background, transparent earth amber, which contains fragments of detritus and isolated large gas bubbles which are perfectly visible against its transparent yellow-brown background, green amber and mixed earth amber, where there are fragments of opaque yellow amber and amber with isolated plant impurities.

Secondary varieties
 Air, light, changes in humidity and temperature all cause primary amber varieties to change their colour and internal structure to become secondary varieties. The change in colour means going from yellow to red or orange. The change in internal structure means numerous cracks appearing inside the nugget, which leads to the formation of the so-called “sugar” structure. Amber also gets covered by a weathered layer of “bark,” while its surface becomes uneven and rough. Amber nuggets which have long remained in sediments above the surface of ground waters are the most weathered. Specimens which come from old collections or which have been subject to air and light for a long time, which is often the case with specimens on display, also change their colour from yellow to red and orange or from white to yellowish. Among secondary varieties we differentiate red amber, which is red or orange in colour, amber called glimmer amber, which is transparent red, and the sugar amber referred to above, in which a grid of fine cracks makes it akin to a sugar cube.

We can clearly see the diversity of raw amber varieties depending on their place of origin. Amber from Sambia is less diverse, with opaque yellow varieties predominating. Amber from the Baltic, from Holocene beach mines or from Pleistocene sediments in the Kurpie region, features a great abundance of varieties. These differences are caused by the conditions in which the amber nuggets lay. Sambian amber lay in the so-called blue earth, where it accumulated, for at least 40 million years in conditions which were conducive to its conservation and therefore its varieties did not diversify. In contrast, amber obtained in Poland changed its place of accumulation several times and was deposited in ever younger sediments in its journey from Tertiary to Pleistocene and Holocene sediments. The changing conditions in the sediments and amber’s long journeys brought about the great diversification of amber varieties. This is why raw amber from Polish deposits has the full range of varieties, which makes it so sought-after by artists.

Real but unnatural
 Amber, defined as real (or improved) but already unnatural, is a separate problem. This is amber which has been transformed during treatment. The reason for this transformation of amber is chiefly fashion for specific “amber varieties.” And so, for instance, amber is often subject to thermal processing in autoclaves, which changes its colour and degree of transparency and results in transparent amber. However, no artificially-obtained variety can replace the beautiful, natural varieties of amber, in which the clusters of gas bubbles and various shades of colour create beautiful and mysterious landscapes in the nuggets.