Amber

Amber (or, technically, resinite) is fossilized tree resin (not sap), which has been appreciated for its color and natural organic beauty since Neolithic times. The two substances were confused because they both were found washed up on beaches. Ambergris is lighter than water and floats; whereas amber is lighter than stone, but not light enough 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 theorise 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 (In German it is Bernstein, in Dutch it is barnsteen etc.). 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. 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. The nodules from the blue earth have to be freed from matrix and divested of their opaque crust, 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 the 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".

Counterfeit amber

Often amber (particularly with insect inclusions) is counterfeited using a plastic resin. A simple test consists of touching the object with a heated pin and determining if the resultant odor is of wood resin. If not, the object is counterfeit, although a positive test may not be conclusive owing to a thin coat of real resin. Generally counterfeits will have a too-perfect pose and position of the trapped insect.

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.

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.

Ia:
Includes Succinite (= 'normal' Baltic amber) and Glessite.

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

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.

Geological record

The oldest amber recovered dates to the Upper Carboniferous period (). Its chemical composition makes it difficult to match the amber to its producers - it is most similar to the resins produced by flowering plants, which did not evolve until the Jurassic, around . Amber becomes abundant soon afterwards, in the Early Cretaceous, , It appears, however, to have been partly derived from yet earlier Tertiary deposits (Eocene); and it occurs also as a derivative phase in later formations, such as glacial drift. Relics of an abundant flora occur as inclusions trapped within the amber while the resin was yet fresh, suggesting relations with the flora of Eastern Asia and the southern part of North America. Heinrich Göppert named the common amber-yielding pine of the Baltic forests Pinites succiniter, but as the wood does not seem to differ from that of the existing genus it has been also called Pinus succinifera. It is improbable, however, that the production of amber was limited to a single species; and indeed a large number of conifers belonging to different genera are represented in the amber-flora.

Paleontological significance

Amber is a unique preservational mode, preserving otherwise unfossilizable parts of organisms; as such it is helpful in the reconstruction of ecosystems and organisms.

The chemical composition of the resin is, unfortunately, of limited utility in reconstructing the phylogenetic affinity of the resin producer. crustaceans, bacteria and amoebae, marine microfossils, wood, flowers and fruit, hair, feathers and other small organisms have been recovered in ambers dating to . Amber's place in culture and tradition lends it a tourism value; Palanga Amber Museum is dedicated to the mineral.

Historic medicinal uses

Amber has long been used in folk medicine for its purported healing properties. Amber and extracts were used from the time of Hippocrates in ancient Greece for a wide variety of treatments through the Middle Ages and up until the early twentieth century. Prior to World War II amber was widely used in Germany for teething problems. Although when burned, amber does give off a characteristic "pinewood" fragrance, modern products, such as perfume, do not normally use actual amber. This is due to the fact that fossilized amber produces very little scent. In perfumery, scents referred to as “amber” are often created and patented to emulate the opulent golden warmth of the fossil. The modern name for amber is thought to come from the Arabic word, ambar, meaning ambergris. The term “amber” is loosely used to describe a scent that is warm, musky, rich and honey-like, and also somewhat oriental and earthy. It can be synthetically created or derived from natural resins. When derived from natural resins it is most often created out of labdanum. Benzoin is usually part of the recipe. Vanilla and cloves are sometimes used to enhance the aroma.

"Amber" perfumes may be created using combinations of labdanum, benzoin resin, copal (itself a type of tree resin used in incense manufacture), vanilla, Dammara resin and/or synthetic materials.

See also

List of types of amber

Ammolite

Copal

Oil of amber

Amber Road

Amber Room

Pearl

Precious coral

References

Azar, D. (2000). Les ambres Mésozoïques du Liban. Doctoral thesis. Universite Paris XI Orsay, France, 202 pp. Kaddumi, H. F. 2007: Amber of Jordan, the Oldest Prehistoric Insects in Fossilized Resin, Third edition. Publications of the Eternal River Museum of Natural History, Amman. 298 pp.

External links

Farlang many full text historical references on Amber Theophrastus, George Frederick Kunz, and special on Baltic amber.

IPS Publications on amber inclusions International Paleoentomological Society: Scientific Articles on amber and its inclusions

Webmineral on Amber Physical properties and mineralogical information

Mindat Amber Image and locality information on amber

NY Times 40 million year old extinct bee in Dominican amber

Category:Arabic words and phrases Category:Fossil resins Category:Gemstones Category:Amorphous solids