dimanche 14 octobre 2012

How Is Amber Produced?

Several factors affect the production of amber from resin, a process known as amberization. Once the resin is exuded it hardens. Resin contains liquids such as oils, acids and alcohols, including the aromatic compounds that produce the distinctive resinous smell – two examples of highly aromatic resins are frankincense and myrrh. Scientists call these liquids volatiles and they dissipate and evaporate from the resin. The resin then undergoes a process known as polymerization, whereby the organic molecules join to form much larger ones called polymers. Hardened resin is known as copal. Copal becomes incorporated into soil and sediments where it remains long after the tree dies. It continues to polymerize and lose volatiles until the resultant amber is completely polymerized, has no volatiles and is inert.

Frankincense tree

Many scientists thought that time was important in the fossilization of resin to produce amber, and the amberization process was estimated as taking between 2 and 10 million years. However, it now appears that many more factors are involved. Most amber in deposits around the world was not formed where it is found – the copal or amber has been eroded from the soil, transported by rivers and deposited elsewhere. For instance, amber from Borneo is 12 million years old and comes from sand and clay sediments that were deposited in a deep ocean. The fossilized resin from Borneo that comes from beds of sandstone is completely inert and undoubtedly amber. However, resin that comes from beds of clay still contains volatile components, which means that it is still copal. So, the type of sediment in which the resin is deposited is much more important than time for amber formation. But what is not so clear is the effect of water and sediment chemistry on the resin.

Resin oozing from under the bark of a cedar tree, where a branch has been sawn off

From Amber: The Natural Time Capsule
By Andrew Ross

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