Amber

Amber is fossilised tree resin (not sap), which has been appreciated for its color and natural beauty since Neolithic times.

Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects.

Amber is used as an ingredient in perfumes, as a healing agent in folk medicine, and as jewellery.

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An ant in amber. image: Anders L. Damgaard /wikipedia

There are five classes of amber, defined on the basis of their chemical constituents. (see further down the page for these types)

What is the origin of the word amber?

The English word amber derives from Arabic ʿanbar عنبر‎ (cognate with Middle Persian ambar ) via Middle Latin ambar and Middle French ambre. The word was adopted in Middle English in the 14th century as referring to what is now known as ambergris (ambre gris or "grey amber"), a solid waxy substance derived from the sperm whale. 

In the Romance languages, the sense of the word had come to be extended to Baltic amber (fossil resin) from as early as the late 13th century. At first called white or yellow amber (ambre jaune), this meaning was adopted in English by the early 15th century. As the use of ambergris waned, this became the main sense of the word.

The two substances ("yellow amber" and "grey amber") conceivably became associated or confused because they both were found washed up on beaches. 

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Typical beach sand on the Baltic where amber is washed up. image: wikimedia


Ambergris is less dense than water and floats, whereas amber is too dense to float, though less dense than stone. 

What about amber and the origin of the term electricity?

The classical names for amber, Latin electrum and Ancient Greek ἤλεκτρον (ēlektron), are connected to a term ἠλέκτωρ (ēlektōr) meaning "beaming Sun”. According to myth, when Phaëton son of Helios (the Sun) was killed, his mourning sisters became poplar trees, and their tears became elektron, amber.

Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber, could be rubbed with cat's fur to attract light objects like feathers. Thales of Miletus made a series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing.


How is amber classified?

Amber can be classified into several forms. Most fundamentally, there are two types of plant resin with the potential for fossilization. 

  • Terpenoids, produced by conifers and angiosperms, consist of ring structures formed of isoprene (C5H8) units.  
  • Phenolic resins are today only produced by angiosperms, and tend to serve functional uses. 
  • The extinct medullosans produced a third type of resin, which is often found as amber within their veins.


The composition of resins is highly variable; each species produces a unique blend of chemicals which can be identified by the use of pyrolysis–gas chromatography–mass spectrometry. 

 The overall chemical and structural composition is used to divide ambers into five classes .


  • Class I
    • This class is by far the most abundant. It comprises labdatriene carboxylic acids such as communic or ozic acids.  It is further split into three sub-classes. Classes Ia and Ib utilize regular labdanoid diterpenes (e.g. communic acid, communol, biformenes), while Ic uses enantio labdanoids (ozic acid, ozol, enantio biformenes)
  • Class II
    • These ambers are formed from resins with a sesquiterpenoid base, such as cadinene
  • Class III
    • These ambers are polystyrenes
  • Class IV
    • These are something of a wastebasket; its ambers are not polymerized, but mainly consist of cedrene-based sesquiterpenoids
  • Class V
    • These resins are considered to be produced by a pine or pine relative. They comprise a mixture of diterpinoid resins and n-alkyl compounds. Their main variety is Highgate copalite


There is also a separate classification of amber gemstones, according to the way of production.

Inclusions

Because it originates as a soft, sticky tree resin, amber sometimes contains animal and plant material as inclusions. 

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Typical example of inclusions in amber. image: wikipedia/John Alan Elson - http://www.3dham.com/miscpics/

Amber occurring in coal seams is also called resinite, and the term ambrite is applied to that found specifically within New Zealand coal seams.


source: Amber. (2014, September 5). In Wikipedia, The Free Encyclopedia. Retrieved 10:22, September 9, 2014, from http://en.wikipedia.org/w/index.php?title=Amber&oldid=624325063