Cambridge & Great Eastern Regional Group

SCI Members' News

Amber: Nature's valuable time capsule

Amber is the fossilised resin of ancient trees. Using a host of beautiful images, Andrew Ross introduced this extraordinary and scientifically fascinating material at the CaGE Regional Group lecture at Cambridge University on 19 January 2006. The resin is remarkable for its ability to preserve prehistoric organic remains for millions of years, and many different animal and plant species have been found preserved within it. These remains can tell us a surprising amount about the past. The oldest amber is about 300 million years old; however, the oldest containing insects is 130 million years old. Most amber used in jewellery comes from the Baltic States or from Dominica.

Ross described how to distinguish genuine amber from fake. Most genuine amber jewellery contains circular cracks called sun spangles, which are produced artificially by heating the resin. In a genuine necklace every bead is usually slightly different. There are some additional visual features to distinguish genuine Baltic amber. It often contains clumps of tiny hairs, which would have come from the flowers of oak trees, and black cracks that are filled with tiny pyrite crystals. Some insects in Baltic amber are covered with a white coating which is a product of decay. These features can indicate that a piece is genuine.

There are several tests to distinguish between amber and fake materials such as copal, though these should only be used as a last resort as they are potentially destructive:

• The alcohol test: put a drip of alcohol (such as isopropanol or ethanol) on the surface and let it evaporate. If the surface becomes sticky then it is copal.
• The scratch test: try to scratch it with a pin. If it does not scratch then it is glass.
• The hot wire test: heat up a wire and press it against the surface, which will burn and produce smoke. If the smoke smells resinous, it is either amber or copal; if not it will smell of burnt plastic.
• The salt water test: add seven heaped tea spoons of table salt to half a pint of water and stir for seven minutes. Drop the specimen in the water. If it floats then it is amber, copal or polystyrene.

Amber with large, perfect inclusions is highly sought after, and authenticity must be carefully established. So although amber can trap and preserve creatures with extraordinary clarity, it must be scrutinised with great care. Ross’ discovery that an important specimen in the Natural History Museum’s collection was a Victorian fake led to a flurry of media interest concerning the so-called ‘Piltdown fly’.

The unique and almost perfect specimen of Fannia scalaris preserved in amber was thought to have originated from the Baltic region some 38 million years ago. Since its re-discovery in the 1960s it had acquired considerable scientific fame, not only as the oldest known representative of the housefly family, the Muscidae, but as an important example of a species that had survived unchanged for millennia.

The amber had been cut in half, hollowed out on one side, a fly had been inserted and it been glued back together ... the forgery had lain undetected for more than 80 years

In 1993 he was examining the fossil fly using a binocular microscope and anglepoise lamp. The heat from the lamp warmed the specimen, causing a crack to appear around the fly. Closer examination revealed that the amber had been cut in half, hollowed out on one side, a fly had been inserted and it been glued back together. Hidden among the thousands of amber specimens in the museum’s collections, the forgery had lain undetected for more than 80 years.

Detail of wing

To close the lecture, Ross recounted the real-life efforts to extract intact DNA from insect inclusions, as made famous in fiction by Michael Crichton and the Hollywood blockbuster Jurassic Park. The interest sparked by the film led to several scientific investigations, and one reported finding intact DNA. Unfortunately, it is now widely believed that this was due to contamination. Most scientists are now convinced that DNA is very unlikely to survive intact for such long periods, even in amber.

John Wilkins
Honorary Secretary
Cambridge & Great Eastern Regional Group

* Andrew Ross has written a book, Amber: the natural time capsule, and has appeared in the media. He was an expert consultant on David Attenborough’s television documentary The amber time machine.