About Amber

Amber is fossilized tree resin (not sap), which has been appreciated for its color and natural beauty since Neolithic times. Amber is used as an ingredient in perfumes, as a healing agent in folk medicine, and as jewelry. There are five classes of amber, defined on the basis of their chemical constituents. Because it originates as a soft, sticky tree resin, amber sometimes contains animal and plant material as inclusions. Amber occurring in coal seams is also called resinite, and the term ambrite is applied to that found specifically within New Zealand coal seams.



History and etymology
The English word amber derives from the Arabic 'anbar, via Medieval Latin ambar and Old French ambre. The word originally referred to a precious oil derived from the Sperm whale (now called ambergris). The sense was extended to fossil resin circa 1400, and this became the main sense as the use of ambergris waned. The two substances were confused because they both were found washed up on beaches. Ambergris is less dense than water and floats; whereas amber is less dense than stone, but too dense to float. The word "ambar" was brought to Europe by the Crusaders. In French "ambre gris" was then distinguished from "ambre jaune": ambre gris (gray amber) was ambergris; ambre jaune (yellow amber) was the fossil resin we now call amber.

Amber is discussed by Theophrastus, possibly the first historical mention of the material, in the 4th century BC. The Greek name for amber was ηλεκτρον (electron) and was connected to the Sun God, one of whose titles was Elector or the Awakener. The modern terms "electricity" and "electron" derive from the Greek word for amber and come from William Gilbert's research showing that amber could attract other substances. The word "electron" was coined in 1891 by the Irish physicist George Stoney whilst analyzing elementary charges for the first time.

The presence of insects in amber was noticed by Pliny the Elder in his Naturalis Historia, and led him to theorize correctly that, at some point, amber had to be in a liquid state to cover the bodies of insects. Hence he gave it the expressive name of succinum or gum-stone, a name that is still in use today to describe succinic acid as well as succinite, a term given to a particular type of amber by James Dwight Dana (see below under Baltic Amber).

Heating amber will soften it and eventually it will burn, which is why in Germanic languages the word for amber is a literal translation of burn-Stone (nl. barnsteen, de. Bernstein, the latter of which the Polish word bursztyn derives from). Heated above 200°C, amber suffers decomposition, yielding an "oil of amber", and leaving a black residue which is known as "amber colophony", or "amber pitch"; when dissolved in oil of turpentine or in linseed oil this forms "amber varnish" or "amber lac".

Amber from the Baltic Sea has been extensively traded since antiquity and in the main land, from where amber was traded 2000 years ago, the natives called it glaes (referring to its see-through similarity to glass).

The Baltic Lithuanian term for amber is Gintaras and Latvian Dzintars. They and the Slavic jantar are thought to originate from Phoenician jainitar (sea-resin). However, while most Slavic languages, such as Russian and Czech, retain the old Slavic word, in the Polish language, despite still being correct, jantar is used very rarely (even considered archaic) and was replaced by the word bursztyn deriving from the German analogue.

Composition and formation
Amber is heterogeneous in composition, but consists of several resinous bodies more or less soluble in alcohol, ether and chloroform, associated with an insoluble bituminous substance. Amber is a macromolecule by free radical polymerization of several precursors in the labdane family, e.g. communic acid, cummunol, and biformene. These labdanes are diterpenes (C20H32) and trienes, equipping the organic skeleton with three alkene groups for polymerization. As amber matures over the years, more polymerization takes place as well as isomerization reactions, crosslinking and cyclization.
The average composition of amber leads to the general formula C10H16O.

Formation

Molecular polymerization, resulting from high pressures and temperatures produced by overlying sediment, transforms the resin first into copal. Sustained heat and pressure drives off terpenes and results in the formation of amber.

Botanical Origin

Fossil resins from Europe fall into two categories, the famous Baltic ambers and another that resembles the Agathis group. Fossil resins from the Americas and Africa are closely related to the modern genus Hymenaea.

Inclusions

The abnormal development of resin has been called succinosis. Impurities are quite often present, especially when the resin dropped on to the ground, so that the material may be useless except for varnish-making, whence the impure amber is called firniss. Enclosures of pyrites may give a bluish color to amber. The so-called black amber is only a kind of jet. Bony amber owes its cloudy opacity to minute bubbles in the interior of the resin.

In darkly clouded and even opaque amber, inclusions can be imaged using high-energy, high-contrast, high-resolution X-rays.



Extraction and processing

Distribution and mining
Amber is globally distributed, mainly in rocks of Cretaceous age or younger. Historically, the coast around Königsberg in Prussia was the world's leading source of amber. About 90% of the world's extractable amber is still located in the Kaliningrad Oblast of Russia on the Baltic Sea (which was previously Königsberg in Prussia, before World War II).

Pieces of amber torn from the seafloor are cast up by the waves, and collected by hand, dredging, or diving. Elsewhere, amber is mined, both in open works and underground galleries. Then nodules of blue earth have to be removed and an opaque crust must be cleaned off, which can be done in revolving barrels containing sand and water. Erosion removes this crust from sea-worn amber.

Dominican amber, especially Dominican blue amber, is mined through bell pitting, which is dangerous due to the risk of tunnel collapse.

Treatment
The Vienna amber factories, which use pale amber to manufacture pipes and other smoking tools, turn it on a lathe and polish it with whitening and water or with rotten stone and oil. The final lustre is given by friction with flannel.

When gradually heated in an oil-bath, amber becomes soft and flexible. Two pieces of amber may be united by smearing the surfaces with linseed oil, heating them, and then pressing them together while hot. Cloudy amber may be clarified in an oil-bath, as the oil fills the numerous pores to which the turbidity is due. Small fragments, formerly thrown away or used only for varnish, are now used on a large scale in the formation of "amberoid" or "pressed amber". The pieces are carefully heated with exclusion of air and then compressed into a uniform mass by intense hydraulic pressure; the softened amber being forced through holes in a metal plate. The product is extensively used for the production of cheap jewelry and articles for smoking. This pressed amber yields brilliant interference colors in polarized light. Amber has often been imitated by other resins like copal and kauri, as well as by celluloid and even glass. Baltic amber is sometimes colored artificially, but also called "true amber".

Appearance
Amber occurs in a range of different colors. As well as the usual yellow-orange-brown that is associated with the color "amber", amber itself can range from a whitish color through a pale lemon yellow, to brown and almost black. Other more uncommon colors include red amber (sometimes known as "cherry amber"), green amber, and even blue amber, which is rare and highly sought after.

Much of the most highly-prized amber is transparent, in contrast to the very common cloudy amber and opaque amber. Opaque amber contains numerous minute bubbles. This kind of amber is known as "bony amber".

Although all Dominican amber is fluorescent, the rarest Dominican amber is blue amber. It turns blue in natural sunlight and any other partially or wholly ultraviolet light source. In long-wave UV light it has a very strong reflection, almost white. Only about 100 kg is found per year, which makes it valuable and expensive.[16]

Sometimes amber retains the form of drops and stalactites, just as it exuded from the ducts and receptacles of the injured trees. It is thought that, in addition to exuding onto the surface of the tree, amber resin also originally flowed into hollow cavities or cracks within trees, thereby leading to the development of large lumps of amber of irregular form.

Classification
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 spectroscopy. The overall chemical and structural composition is used to divide ambers into five classes. There is also a separate classifications of amber gemstones, according to the way of production.

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 utilise regular labdanoid diterpenes (e.g. communic acid, communol, biformenes), whilst Ic uses enantio labdanoids (ozic acid, ozol, enantio biformenes).

Ia:
Includes Succinite (= 'normal' Baltic amber) and Glessite. Have a communic acid base. They also include much succinic acid.

Baltic amber yields on dry distillation succinic acid, the proportion varying from about 3% to 8%, and being greatest in the pale opaque or bony varieties. The aromatic and irritating fumes emitted by burning amber are mainly due to this acid. Baltic amber is distinguished by its yield of succinic acid, hence the name succinite. Succinite has a hardness between 2 and 3, which is rather greater than that of many other fossil resins. Its specific gravity varies from 1.05 to 1.10. It can be distinguished from other ambers via IR spectroscopy due to a specific carbonyl absorption peak. IR spectroscopy can detect the relative age of an amber sample. Succinic acid may not be an original component of amber, but rather a degradation product of abietic acid.

Ib:
Like class Ia ambers, these are based on communic acid; however, they lack succinic acid.

Ic:
This class is mainly based on enantio-labdatrienonic acids, such as ozic and zanzibaric acids. Its most familiar representative is Dominican amber.

Dominican amber differentiates itself from Baltic amber by being mostly transparent and often containing a higher number of fossil inclusions. This has enabled the detailed reconstruction of the ecosystem of a long-vanished tropical forest. Resin from the extinct species Hymenaea protera is the source of Dominican amber and probably of most amber found in the tropics. It is not "succinite" but "retinite".

Class II:
These ambers are formed from resins with a sesquiterpenoid base, such as cadinene.

Class III:
These ambers are polystyrenes.

Class IV:
This class is something of a wastebasket; its ambers are not polymerized, but mainly consist of cedarane-based sesquiterpenoids.

Class V:
Class V resins are considered to be produced by a pine or pine relative. They comprise a mixture of diterpinoid resins and n-alkyl compounds. Their type mineral is highgate copalite.

Classification of Baltic amber (succinite) gemstones by the International Amber Association
Natural Baltic amber – gemstone which has undergone mechanical treatment only (for instance: grinding, cutting, turning or polishing) without any change to its natural properties

Modified Baltic amber – gemstone subjected only to thermal or high-pressure treatment, which changed its physical properties, including the degree of transparency and color, or shaped under similar conditions out of one nugget, previously cut to the required size.

Reconstructed (pressed) Baltic amber – gemstone made of Baltic amber pieces pressed in high temperature and under high pressure without additional components.

Bonded Baltic amber – gemstone consisting of two or more parts of natural, modified or reconstructed Baltic amber bonded together with the use of the smallest possible amount of a colorless binding agent necessary to join the pieces.