Amber has a deep fascination for man 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 captures our imagination.
Amber is found all over the world. This short narrative looks at some aspects of amber which might interest both the casual and the informed reader.
Formation of Amber
Amber begins as resin exuded from trees millions of years ago. All known deposits of amber come from various tree species which are now extinct. Baltic amber was produced by a tree called Pinites succinifer, a tree sharing many characteristics of the currently living species Pseudolarix. In appearance it would have looked something 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 would begin to go through a number of stages in order to become amber.
The first stage involved the slow evaporation of volatile oils. The oils, called turpenes, could take anything from a 100 to a 1000 years to fully dissipate. Once completed the resin would become harder and could then be called copal.
Columbia in South America has extensive deposits of copal which is frequently sold as amber, but 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.
Following the dispersal of the oils the next stage is the cross chain linking of the molecular structure within the copal. Almost a kind of polymerisation. This makes the copal harder and less brittle. This second stage may take millions of years before the process turns the copal into something approaching the structure of amber.
It is speculated that either one or both of these stages in the formation of amber must take place in an anaerobic environment, or it may have to sustain a period of immersion in sea water. Amber which is exposed to air for several years undergoes oxidation which causes a distinct darkening and crusting of the gems surface. If sustained over millions of years the amber can fragment and breakdown into small tiny splinters and shards. The Isle Of Wight (UK) amber is amongst the oldest found in the world, an estimated 120 Million years. Not surprisingly the pieces found are small and tiny weighing only a few grams. Lebanese deposits dating back 125 million years are similarly found in minuscule sizes and quantities. Baltic amber (a mere 40 millions years old) can be found in quite large blockss, in some cases weighing several kilos.
Facts About Amber
The quantities of the of resin which must have been generated in the Baltic deposits was phenomenal. This can be confirmed simply from the amount of amber that has been extracted from various Baltic mines. The Palmnicken factory , a German government controlled company extracted in 1925 a record 1,205,916 pounds.
Commercial mining and gathering activities have been recorded from as early as 1264 AD and in various guises continues to this day. Imagine, how much amber has been extracted over a period of 700+ years? It is also true to state that the majority of this extraction was subsequently turned into varnish and shellac. 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 located further South. The resin was subsequently carried North probably by two great rivers from its original site and deposited in a great esturial drift of silt and clay. This deposit site extends out under the sea and stops short of the East Anglia coast. This is the source of amber washed up onto the Norfolk, Suffolk beaches. Autumn and Spring storms together with complimenting tides tears pieces of raw amber from the sea bed and strands them on the shore line. If you look for amber its usually mixed in with the stranded seaweed, litter and of course 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. The reason for this wide variation is simply because amber is not a true mineral, it is a compound with variable mixtures, consequently no precise quantification can be made with any exactitude. Some aspects of amber are fairly consistent. On Moh’s scale of hardness it lies between 2 and 2.5. It has a refraction index of 1.54 and a melting point between 150 – 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 – 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 what ever process, the resin is impregnated with none native compounds and given its distinct hue.
The claim of strong fluorescence in amber is often exaggerated. Generally, the fluorescence is weak and photographs which show glowing pieces of amber are usually achieved with exposure times in excess of 2 minutes under strong UV lamps, quite misleading.
Inclusions in Amber
One of the most exciting and interesting aspects of amber are the inclusions which are often found within it, these are both flora and fauna in type.
The most frequent inclusions to be found in amber, particularly Baltic are examples of the Diptera Family, or true flies. Quite often these are Mycetophilidea species, often referred to as fungus gnats. These tiny little flies would have 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 this insight into the ecology of ancient times which makes it so fascinating and compelling to study. It should also be recognised that amber gives us a skewed view of this ancient world. For example, it is unusual for instance to find cockroaches in amber. But, Blattoidea most certainly did exist as every stage of pupation is present within the amber record, but why so few adults? The reason is quite simple; cockroaches were big enough and large enough to pull themselves out of the resin. Analysis therefore 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 which infrequently turn up in amber. Occasionally a small lizard will be found, trapped and encased in amber, particularly from the Dominican Republic deposits. The AMNH have a famous example of a 25,000,000 year old gecko. Lizards are extremely rare in European deposits. The author believes there have only been two known and verified instances of lizards preserved in Baltic amber.
Another unusual find are 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 animal can be seen but most of the flesh has deteriorated and several bones are exposed, some broken. Under closer scrutiny a review of the bones suggested that this particular frog must have had at least 6 legs. Palaeontologists speculate that a bird who ate the frogs may have had a feeding site, perhaps on a branch directly above an accumulating pool of resin. Hence the numerous bones present. The complete frog was perhaps an unlucky drop by the bird when it alighted on the branch.
Mammalian animals have left their mark in the amber record. Their hair can infrequently be found trapped as tufts or single strands. When found in Baltic amber it is often attributed to Sloths who lived within the ancient forest. The author has in his possession a piece of amber which has strands of hair which have been identified as that of a mole. One can only guess how they came to be trapped within the amber.
Doctor Kosmowska-Ceranowicz has describes a large set of mammalian molars which were discovered encased in Polish amber. The teeth have been perfectly ‘amberised’ and it is thought that a 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 thus preserving the set of teeth.
Resin whilst in the process of hardening usually develops a skin whilst the internal composite is still soft. Occasionally amber of this nature has impressions stamped on its surface and thus becomes a trace fossil. In one such piece the impression of a cats 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 has completely re written the standing theory of the population of the West Indian islands by land animals. Yet again another remarkable insight into the ancient evolution and development of life through the window of amber.
The faking of inclusions of amber has been a major cottage industry since the earliest times. This perhaps reached its height in the early 1900 and a major source was from New Zealand. The North Island has some major deposits of Kaori Gum, and at the turn of the 19 century some was used to fake and imitate true amber. The digging of Kaori Gum was such a major industry in fact the workers even had their own newspaper; ‘The Gum Diggers Gazette’.
The Kaori Gum would be melted gently and a suitable inclusions placed into the matrix, this was frequently some kind of colourful insect. Colour is always a dead give away of a bogus amber fossil. Truly ancient amber fossils have no colour pigmentation left at all and are usually monotone. However, beetle colour is often an effect of light refraction, i.e. the light being broken into its spectrum elements, the resin however prevents this. By removing the amber from the back of amberised beetles it has been reported that the original colour returns after 40 million years, quite amazing.
One of the cleverest fakes the author has encountered involves 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 which was in fact contemporary to the time of the faking. The offending insect was then surrounded by molten resin and the previously sawn of section placed back in position and glued with the same liquid resin. The result was externaly a perfect piece of amber which passed all tests for true amber.
Most of our understanding, beliefs and research on amber has been based upon the work of European and American culture. The Chinese shared our fascination with amber and the earliest written references go back to A.D. 92. They believed that amber was the soul of tiger which had died and passed into the earth and the Tibetans had perhaps the most beautiful name for this gem; p/-she, which meant perfumed crystal.
Amber is a strange and attractive gem. Its golden transparency lends it a quality which even diamonds do not share. For the artisan it provides a remarkable medium to work with and 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.