Amber: Frozen moments in time
Gary Platt (UK)
Amber has a deep fascination for people, both as a gem and as a chance to look back into the past with a remarkable clarity. Its warm, lustrous touch beguiles us and the remarkable inclusions sometimes found within it capture our imagination.
Amber is found all over the world including, nearer to home, the Isle of Wight. This article looks at some aspects of amber that might interest both the casual and the informed reader.
Formation of amber
Amber begins as resin exuded from trees millions of years ago. Most known deposits of amber come from various tree species that are now extinct. Baltic amber was produced by a tree called Pinites succinifer, a tree sharing many characteristics of the modern genus Pseudolarix. In appearance, it would have looked similar to a pine or spruce tree.
The resin may have originally been used as a defensive mechanism against insect infestation or fungal attack. Once released from the tree, the resin begins to go through a number of stages to become amber.
The first stage involves the evaporation of volatile oils. The oils, called “turpenes”, slowly permeate out of the amber. This may take many thousands of years before the process turns the resin into something approaching the structure of amber. Turpenes give resin its distinctive and powerful odour.
Following the evaporation of the turpene, the next stage is the slow, cross chain linking of the molecular structure within the resin (a kind of polymerisation). This makes the resin hard and brittle compared to its original state of soft plasticity. Once completed, the resin can be called “amber”. Before this final transition stage is complete, the resin may be called “copal”. However, many researchers argue about when resin should be referred to as “copal” or “amber”.
Columbia, in South America, has extensive deposits of copal that are frequently sold as amber. However, recent tests undertaken by G. Poinar have shown that, in some cases, it is less than 250 years old. Madagascar and Kenya also have highly fossiliferous copal mines. Their age is likely to be roughly the same as the Colombian deposits, if not younger.
It is speculated that either one or both of the stages in the formation of amber must take place either in an anaerobic environment (that is, in the absence of oxygen) or it may have to sustain a period of immersion in seawater. Amber, which is exposed to air for several years, undergoes oxidation that causes a distinct darkening and crusting of the gem’s surface. If sustained over many years, the amber can fragment into small splinters and shards. The Isle of Wight amber is amongst the oldest found in the World, an estimated 120 million years old. Not surprisingly, the pieces found are tiny, weighing only a few grams. Lebanese deposits, dating back 125 million years, are similarly found in minuscule sizes and quantities whereas Baltic amber (a mere 40 millions years old) can be found in quite large blocks, in some cases weighing several kilos.
Facts about amber
The largest known piece of Baltic amber ever found weighed 21.5lbs. It was found near Stettin in Poland in 1860 and now resides in the Museum fur Naturkunde in Berlin. Unconfirmed reports exist of a 4,400lb monster discovered in Samland in 1862, but this may be nothing more than a story.
The largest confirmed piece of amber ever found is not from the Baltic but from Borneo. The stone weighed 150lbs, but was unfortunately broken into four pieces during or after extraction.
The quantity of resin from the Baltic deposits is phenomenal. This can be confirmed simply from the amount of amber that has been extracted from various Baltic mines. For example, in 1925, the Palmnicken factory (a German government-controlled company) extracted a record 1,205,916lbs.
Commercial mining and gathering activities have been recorded from as early as 1264AD and, in various guises, continue to this day. Imagine, how much amber has been extracted over a period of 700+ years. It is also true to say that the majority of this extraction was subsequently turned into varnish and shellac, so we will never know what wonders have been lost.
The amber from the Samland Peninsula in the Baltic is actually a secondary deposit. The original, amber forest was probably located further south. The resin was subsequently carried north, probably by two great rivers and deposited in a great, estuarial drift of silt and clay. (At the moment, this is still speculation as many scientists disagree on this point). This deposit extends some way out under the sea and is the probable source of the amber washed up on the Norfolk and Suffolk beaches. Autumn and spring storms, together with the tide, tear pieces of raw amber from the seabed and strand them on the shoreline. If you look for amber, it is usually mixed in with the stranded seaweed, litter and, of course, the obligatory dead seagull.
The chemical structure of amber is not consistent, not even within a single fragment let alone a single deposit. Consequently, numerous chemical formulas have been attributed to it: C10H16O, 13C40H64O14, 12C12H20O and so on. The reason for this wide variation is simply because amber is not a true mineral: it is an organic plastic with variable mixtures. Consequently, no precise quantification can ever be made. However, some aspects of amber are fairly consistent. On Moh’s scale of hardness, it lies between 2 and 2.5. It also has a refraction index of 1.54 and a melting point between 150 oC and 180oC.
The colour range is extremely varied, ranging from near white (osseous) through all shades of yellow, brown and red. There are even examples of blue and green amber. Blue or green amber is thought to have two possible causes: the permeation of raw resin by mineral deposits present either in the soil into which it fell or the settling of volcanic dust and ash onto the resin when it was first secreted. By whatever process, the resin is impregnated with unusual compounds and given its distinct hue.
The claim for strong fluorescence in amber is often exaggerated. Generally, the fluorescence is weak. Photographs showing glowing pieces of amber are usually achieved with exposure times in excess of two minutes under strong UV lamps and are, therefore, quite misleading.
Inclusions in amber
One of the most exciting and interesting aspects of amber is the inclusions that are found within it, both flora and fauna.
The most frequent inclusions, particularly Baltic amber, are examples of the order Diptera, or “true flies”. Quite often, these are species of the superfamily Sciaroidea, commonly referred to as “fungus gnats”. These tiny flies lived on the fungus growing on the rotting vegetation of the amber forest of which, no doubt, there was enough to support an enormous population.
It is this aspect of amber, these frozen moments in time, which give us an insight into the ecology of ancient times and that makes it so fascinating and compelling to study. However, it should also be recognised that amber gives us a skewed view of this ancient world. For example, it is unusual to find cockroaches in amber. But, Blattoidea most certainly did exist, as every stage of moult development is present within the amber record. So why are there so few fully formed adults? The reason is quite simple: cockroaches were big enough to pull themselves out of the resin. Therefore, analysis of the amber deposits needs to be done with a high degree of circumspection, research and reasoned insight.
There are some unusual and extraordinary things that infrequently turn up in amber. Occasionally, a small lizard will be found, particularly from the Dominican Republic. The American Natural History Museum has a famous example of a 25,000,000-year-old gecko. Lizards are extremely rare in European deposits. I believe there have only been two known and verified instances of lizards preserved in Baltic amber. One has since been lost to science, the other is currently for sale (and may, even now, have been sold).
Another unusual find is the remains of a frog discovered in a piece mined in the Dominican Republic. At first, it was thought to be just one animal with some tissue preserved. The distinct shape of the frog can be seen but most of the flesh has deteriorated and several bones are exposed, some broken. Under closer scrutiny, a count of the bones suggested that this particular frog must have had at least six legs! Palaeontologists speculate that a bird, which ate the frogs, may have had a feeding site (perhaps on a branch directly above an accumulating pool of resin) giving rise to the presence of numerous bones. The complete frog was perhaps an unlucky drop by the bird when it alighted on the branch.
Mammals have also left their mark in the amber record. Infrequently, their hair can be found trapped as tufts or single strands. When found in Baltic amber, it is often attributed to Sloths that lived within the ancient forest. I have in my possession a piece of amber that has strands of hair tentatively identified as being from a mole. One can only guess how they came to be trapped within the amber.
Dr Kosmowska-Ceranowicz has described a set of mammalian molars (possibly from a pig) that were discovered encased in Polish amber. The teeth have been perfectly “amberised” and it is thought that the dead animal lay with its face partially lying in a bed of resin. The resin seeped in and around the decaying jaw of the animal and preserved a set of teeth.
While in the process of hardening, resin usually develops a skin while the interior is still soft. Occasionally, amber of this nature has impressions stamped on its surface and, therefore, becomes a trace fossil. In one such piece, the impression of a cat’s paw has clearly been left in a piece of Baltic amber.
During 1996, the spine and ribs of a mouse were discovered in amber from one of the Dominican Republic sites. This discovery completely re-wrote the standing theory of the way land animals populated the West Indian islands. Yet again, this is another remarkable insight into the ancient evolution and development of life through the window of amber.
The Isle of Wight amber deposit has so far yielded several identified insects. These include a Chironomid, a Diptera Midge, and a very interesting Hymenoptera (Wasps). As at the time of writing, the site is partially covered with a mudflow and further collection is problematic. However, it is almost certain that further discoveries have yet to be made.
Fakes
The faking of inclusions of amber has been a major cottage industry since the earliest times. This perhaps reached its height in the early 1900s with a major source being from New Zealand. The North Island has some major deposits of “Kaori Gum” and, at the turn of the 19th century, some of this was used to fake and imitate true amber. The digging of Kaori Gum was such a major industry, the workers even had their own newspaper, The Gum Diggers Gazette.
The Kaori Gum was gently melted and suitable inclusions placed into the matrix. This was frequently some kind of colourful insect. Colour is always a giveaway of a bogus amber fossil. Truly ancient amber fossils have no colour pigmentation left at all and are usually monochromatic. However, the colour of beetles is often an effect of light refraction (that is, the light is broken into its spectral elements). When a beetle is trapped in amber, the resin prevents this for happening. By removing the amber from the back of amberised beetles, it has been reported that the original colour returns after 40 million years, which I think is quite amazing.
One of the cleverest fakes I have encountered involved the use of a true piece of amber. The amber had a section cut from one end of the piece. A hole was then drilled into the main block. Inside this cavity was placed the insect that was, in fact, alive at the time of faking. The offending insect was then surrounded by molten resin and the previously sawn-off section placed back in position and glued with the same liquid resin. The result was externally a perfect piece of amber that passed all tests for true amber.
Conclusion
Most of our understanding and research on amber have been based on the work of European and American cultures. However, the Chinese shared our fascination with amber and the earliest, written references go back to 92AD. They believed that amber was the soul of a tiger that had died and passed into the earth. The Tibetans had perhaps the most beautiful name for this gem “pö-she”, which means, “perfumed crystal”.
Amber is a strange and attractive gem. Its golden transparency lends it a quality that even diamonds do not share. For the artisan, it provides a remarkable medium to work with and to create some of the most beautiful objects for us to enjoy. For the scientist, it provides a glimpse into the past – a window into history.
I would like to acknowledge the help of by Dr Edmund Jarzembowski of Maidstone Museum. In addition, I am always interested in discussing and listening to stories about amber. Therefore, please feel free to contact me through any of the following means: Garry Platt, 81 Buxton Road, Furness Vale, High Peak, Derbyshire, SK23 7PL. Tel. No: 01663 745367. Email: garry@gplatt.demon.co.uk.
Further reading
Grimaldi DA. 1996. Amber Window to the Past. Abrams; Poinar G Jr. 1994. Bees in fossilised resin. Bee World. 75(2): 71-77.
Dahlström A. & Brost L. 1995. The Amber Book. Geoscience Press Inc.
Nicholas CJ, Henwood A & Simpson M. 1993. A new discovery of early Cretaceous (Wealden) amber from the Isle of Wight. Geological Magazine. 130. 847-850.
Kosmowska-Ceranowicz B. & Kulicka R. 1993. Amber Molars. Amber & Fossils. 1 (1) 38-41.
Rice PC. 1987. Amber: The Golden Gem of the Ages. The Kosciuszko Foundation, Inc.