RESIN into AMBER
The process and transformation of resin into amber is not fully understood. But there are one or two elements which are recognised as being essential the following pages concentrate on these areas.
When the resin is initial
exuded it is soft and tacky. The molecular structure consists of
unlinked complex organic compounds. The resin then has two
significant phases through which it must go in order to become
amber, both relate to molecular changes, here portrayed with
simple diagrams. The yellow background colour represents the
general resin matrix, the green dots represent volatile turpene
molecules and the blue dots represent some of the organic
molecules within the resin.
The first change which takes place
within the fossilising resin is the partial polymerisation of the
molecular structure. The molecules begin to cross chain link and
form stronger bonds. In the diagram we can see the molecular
structure becoming more uniform and organised. The resin begins
to take on a harder quality due to this molecular change. When
rubbed vigorously a strong smell of resin is still prelevant as
the sample still contains many volatile oils in the form of
turpenes.This process of polymerisation may take thousands of
years before the resultant material can be called copal.
Contentious arguments have been raised
about whether certain sources are copal or amber. One of the most
fiercely debated deposits is that found in South America, Colombia,
Santander. George
Poinar has proved that this particular source is very
definitely copal and not amber.
The second stage involves the evaporation of volatile oils trapped within the resin its self. In this diagram the volatile oil molecules, known as turpenes are shown as green dots. They can be seen escaping from the matrix of the resin shown in yellow.
The length of time needed to reach the point at which the majority of turpenes have escaped varies dependant upon surrounding conditions and the nature of the resin at the moment of its formation. It is known that this process can take millions of years.
In brief the process follows this development:
It should be noted that although the rate of transition from resin to amber is shown as a straight linear process, in reality it is variable and not at all a regular transitional mechanism.
There is one other known factor that must be present for the
transformation of resin into amber to be successful. It is an
anaerobic environment for most if not all of the transformational
stages. Oxygen when its comes into contact with fossilising resin
slowly begins to oxides its surface. This corrosive effect on the
resin can progress through the entire structure until finally
nothing but tiny chips and pieces remain. For the most part the
anaerobic environment is achieved through immersion in water,
frequently sea water. The Baltic and Dominican Republic amber
sites both show evidence of long term immersion in a sea water
environment. This has been determined through fossils found in
situ with the amber its self. 
Here is a photograph of a
shell attachment which obviously adhered to the amber over a long
period of immersion, in this particular case, the Baltic sea.
Where amber has lost its anaerobic environment its can very quickly succumb to the effects of oxidation. Even jewellery a few decades old can show the distinct signs of crazing and cracking on its surface which are clear indications of oxygen attacking the amber's surface.
Andrew Ross of the Natural History Museum in London pictured below with part of the useums amber collection informed me in some recent correspondence that the sediment in which the resin is laid down may also play a significant role in the process of 'amberisation'. He makes the following observation:
'The amberisation process appears to be more
complicated. Borneo amber is of Middle Miocene age. Specimens
that come from sandstone beds are dark and undoubtedly true amber
(no reaction with alcohol), however specimens that come from clay
beds of the same age are yellow and are copal (react with
alcohol). Clearly the kind of sediment is very important in this
process'
This issue will be further referred to in his book on amber which is due to published hopefully sometime in 1998.
Very old deposits,dating back to the Cretaceous produce amber in small pieces. Sizes larger than 1-2 cm in diameter are unusual and rare. For the most part they are tiny individual pieces. This is predominately due to the extreme age of these sources and the long term effects of the atmosphere upon the resin once the anaerobic protection ceased.
Heat and pressure may also play a crucial role in the formation of amber. But precisely what mechanisms they support and how they effect the transformation is not fully understood, though it is likely that they impact in some way upon the polymerisation and turpene evaporation process.
