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Friday, August 9, 2024

Petrified wood

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Petrified_wood
Polished slice of a petrified tree from the Late Triassic Epoch (approximately 230 million years ago) found in Arizona. The remains of insects can be detected in an enlarged image.
Petrified log at the Petrified Forest National Park

Petrified wood (from Ancient Greek πέτρα meaning 'rock' or 'stone'; literally 'wood turned into stone'), is the name given to a special type of fossilized wood, the fossilized remains of terrestrial vegetation. Petrifaction is the result of a tree or tree-like plants having been replaced by stone via a mineralization process that often includes permineralization and replacement. The organic materials making up cell walls have been replicated with minerals (mostly silica in the form of opal, chalcedony, or quartz). In some instances, the original structure of the stem tissue may be partially retained. Unlike other plant fossils, which are typically impressions or compressions, petrified wood is a three-dimensional representation of the original organic material.

The petrifaction process occurs underground, when wood becomes buried in water or volcanic ash. The presence of water reduces the availability of oxygen which inhibits aerobic decomposition by bacteria and fungi. Mineral-laden water flowing through the sediments may lead to permineralization, which occurs when minerals precipitate out of solution filling the interiors of cells and other empty spaces. During replacement, the plant's cell walls act as a template for mineralization. There needs to be a balance between the decay of cellulose and lignin and mineral templating for cellular detail to be preserved with fidelity. Most of the organic matter often decomposes, however some of the lignin may remain. Silica in the form of opal-A, can encrust and permeate wood relatively quickly in hot spring environments. However, petrified wood is most commonly associated with trees that were buried in fine grained sediments of deltas and floodplains or volcanic lahars and ash beds. A forest where such material has petrified becomes known as a petrified forest.

Formation

Microscopic view of petrified Callixylon wood
Petrified wood mineralized with carnotite from St. George, Utah
Petrified wood from the Shinarump Formation at the Nacimiento Mine, Cuba, New Mexico. The brown wood at right shows conventional silica mineralization. The black wood at left shows unusual mineralization with chalcocite and other sulfide minerals. The blue-green stains are from oxidation of the chalcocite to azurite and malachite.

Petrified wood forms when woody stems of plants are buried in wet sediments saturated with dissolved minerals. The lack of oxygen slows decay of the wood, allowing minerals to replace cell walls and to fill void spaces in the wood.

Wood is composed mostly of holocellulose (cellulose and hemicellulose) and lignin. Together, these substances make up 95% of the dry composition of wood. Almost half of this is cellulose, which gives wood much of its strength. Cellulose is composed of long chains of polymerized glucose arranged into microfibrils that reinforce the cell walls in the wood. Hemicellulose, a branched polymer of various simple sugars, makes up the majority of the remaining composition of hardwood while lignin, which is a polymer of phenylpropanes, is more abundant in softwood. The hemicellulose and lignin encrust and reinforce the cellulose microfibrils.

Dead wood is normally rapidly decomposed by microorganisms, beginning with the holocellulose. The lignin is hydrophobic (water-repelling) and much slower to decay. The rate of decay is affected by temperature and moisture content, but exclusion of oxygen is the most important factor preserving wood tissue: Organisms that decompose lignin must have oxygen for their life processes. As a result, fossil wood older than Eocene (about 56 million years old or older) has lost almost all its holocellulose, and only lignin remains. In addition to microbial decomposition, wood buried in an alkaline environment is rapidly broken down by inorganic reactions with the alkali.

Wood is preserved from decomposition by rapid entombment in mud, particularly mud formed from volcanic ash. The wood is then mineralized to transform it to stone. Non-mineralized wood has been recovered from Paleozoic formations, particularly Callixylon from Berea Sandstone, but this is very unusual. The petrified wood is later exposed by erosion of surrounding sediments. Non-mineralized fossil wood is rapidly destroyed when exposed by erosion, but petrified wood is quite durable.

Some 40 minerals have been identified in petrified wood, but silica minerals are by far the most important. Calcite and pyrite are much less common, and others are quite rare. Silica binds to the cellulose in cell walls via hydrogen bonding and forms a kind of template. Additional silica then replaces the cellulose as it decomposes, so that cell walls are often preserved in great detail. Thus silicification begins within the cell walls, and the spaces within and between cells are filled with silica more gradually. Over time, almost all the original organic material is lost; only around 10% remains in the petrified wood. The remaining material is nearly pure silica, with only iron, aluminum, and alkali and alkaline earth elements present in more than trace amounts. Iron, calcium, aluminum are the most common, and one or more of these elements may make up more than 1% of the composition.

Just what form the silica initially takes is still a topic of research. There is evidence of initial deposition as opal, which then recrystallizes to quartz over long time periods. On the other hand, there is some evidence that silica is deposited directly as quartz.

Wood can become silicified very rapidly in silica-rich hot springs. While wood petrified in this setting is only a minor part of the geologic record, hot spring deposits are important to paleontologists because such deposits sometimes preserve more delicate plant parts in exquisite detail. These Lagerstätte deposits include the Paleozoic Rhynie Chert and East Kirkton Limestone beds, which record early stages in the evolution of land plants.

Most of the color in petrified wood comes from trace metals. Of these, iron is the most important, and it can produce a range of hues depending on its oxidation state. Chromium produces bright green petrified wood. Variations in color likely reflect different episodes of mineralization. In some cases, variations may come from chromatographic separation of trace metals.

Wood can also be petrified by calcite, as occurs in concretions in coal beds. Wood petrified by calcite tends to retain more of its original organic material. Petrification begins with deposition of goethite in the cell walls, followed by deposition of calcite in the void spaces. Carbonized wood is resistant to silicification and is usually petrified by other minerals. Wood petrified by minerals other than silica minerals tends to accumulate heavy metals, such as uranium, selenium, and germanium, with uranium most common in wood high in lignin and germanium most common in wood preserved in coal beds. Boron, zinc, and phosphorus are anomalously low in fossil wood, suggesting they are leached away or scavenged by microorganisms.

Less commonly, the replacement minerals in petrified wood are chalcocite or other sulfide minerals. These have been mined as copper ore at locations such as the Nacimiento Mine near Cuba, New Mexico.

Simulated petrified wood

Scientists have attempted to duplicate the process of petrification of wood, both to better understand the natural petrification process and for its possible use as a ceramic material. Early attempts used sodium metasilicate as a source of silica, but tetraethyl orthosilicate has proven more promising.

Uses

Table constructed from petrified wood

Petrified wood has limited use in jewelry, but is mostly used for decorative pieces such as book ends, table tops, clock faces, or other ornamental objects. A number of Ancestral Puebloan structures near Petrified Forest National Park were constructed of petrified wood, including the Agate House Pueblo. Petrified wood is also used in New Age healing.

Occurrences

Petrified wood is found worldwide in sedimentary beds ranging in age from the Devonian (about 390 million years ago), when woody plants first appeared on dry land, to nearly the present. Petrified "forests" tend to be either entire ecosystems buried by volcanic eruptions, in which trunks often remain in their growth positions, or accumulations of drift wood in fluvial environments. Amethyst Ridge at Yellowstone National Park shows 27 successive forest ecosystems buried by eruptions, while Petrified Forest National Park is a particularly fine example of fluvial accumulations of driftwood.

Volcanic ash is particularly suitable for preservation of wood, because large quantities of silica are released as the ash weathers. The presence of petrified wood in a sedimentary bed is often an indication of the presence of weathered volcanic ash. Petrified wood can also form in arkosic sediments, rich in feldspar and other minerals that release silica as they break down. The warm supermonsoon climates of the Carboniferous through Permian periods seem to have favored this process. Preservation of petrified forests in volcanic ash beds is less affected by climate and preserves a greater diversity of species.

Areas with a large number of petrified trees include:

Africa

Chunk of petrified wood near El Kurru (Northern Sudan)
Petrified log and Welwitschia at Namibia Petrified forest
  • Egypt – petrified forest in Cairo-Suez road, declared a national protectorate by the ministry of environment, also in the area of New Cairo at the Extension of Nasr City, El Qattamiyya, near El Maadi district, and Al Farafra oasis.
  • Libya – Great Sand Sea – Hundreds of square miles of petrified trunks, branches and other debris mixed with Stone Age artifacts
  • Madagascar – Northwest Coast
  • Namibia – petrified forest of Damaraland
  • Sudan – petrified forest north of El-Kurru

Asia

Oceania

Europe

North America

Petrified logs at Petrified Forest National Park, Arizona, USA

South America

Petrified log in Paleorrota geopark, Brazil
Puyango petrified forest, Ecuador
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Amber

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Amber
An ant inside Baltic amber
Unpolished amber stones

Amber is fossilized tree resin. Examples of it have been appreciated for its color and natural beauty since Neolithic times, and worked as a gemstone since antiquity. Amber is used in jewelry and as a healing agent in folk medicine.

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.

Etymology

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

In the Romance languages, the sense of the word was 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 "gray amber") conceivably became associated or confused because they both were found washed up on beaches. Ambergris is less dense than water and floats, whereas amber is too dense to float, though less dense than stone.

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. The word elektron gave rise to the words electric, electricity, and their relatives because of amber's ability to bear a charge of static electricity.

Pliny the Elder says that the German name of amber was glæsum, "for which reason the Romans, when Germanicus commanded the fleet in those parts, gave to one of these islands the name of Glæsaria, which by the barbarians was known as Austeravia". This is confirmed by the recorded Old High German word glas and by the Old English word glær for "amber" (compare glass). In Middle Low German, amber was known as berne-, barn-, börnstēn (with etymological roots related to "burn" and to "stone"). The Low German term became dominant also in High German by the 18th century, thus modern German Bernstein besides Dutch barnsteen. In the Baltic languages, the Lithuanian term for amber is gintaras and the Latvian dzintars. These words, and the Slavic jantar and Hungarian gyanta ('resin'), are thought to originate from Phoenician jainitar ("sea-resin").

History

Theophrastus discussed amber in the 4th century BCE, as did Pytheas (c. 330 BCE), whose work "On the Ocean" is lost, but was referenced by Pliny, according to whose Natural History:

Pytheas says that the Gutones, a people of Germany, inhabit the shores of an estuary of the Ocean called Mentonomon, their territory extending a distance of six thousand stadia; that, at one day's sail from this territory, is the Isle of Abalus, upon the shores of which, amber is thrown up by the waves in spring, it being an excretion of the sea in a concrete form; as, also, that the inhabitants use this amber by way of fuel, and sell it to their neighbors, the Teutones.

Fishing for amber on the coast of Baltic Sea. Winter storms throw out amber nuggets. Close to Gdańsk, Poland.

Earlier Pliny says that Pytheas refers to a large island—three days' sail from the Scythian coast and called Balcia by Xenophon of Lampsacus (author of a fanciful travel book in Greek)—as Basilia—a name generally equated with Abalus. Given the presence of amber, the island could have been Heligoland, Zealand, the shores of Gdańsk Bay, the Sambia Peninsula or the Curonian Lagoon, which were historically the richest sources of amber in northern Europe. It is assumed that there were well-established trade routes for amber connecting the Baltic with the Mediterranean (known as the "Amber Road"). Pliny states explicitly that the Germans exported amber to Pannonia, from where the Veneti distributed it onwards.

The ancient Italic peoples of southern Italy used to work amber; the National Archaeological Museum of Siritide (Museo Archeologico Nazionale della Siritide) at Policoro in the province of Matera (Basilicata) displays important surviving examples. It has been suggested that amber used in antiquity, as at Mycenae and in the prehistory of the Mediterranean, came from deposits in Sicily.

Wood resin, the source of amber

Pliny also cites the opinion of Nicias (c. 470–413 BCE), according to whom amber

is a liquid produced by the rays of the sun; and that these rays, at the moment of the sun's setting, striking with the greatest force upon the surface of the soil, leave upon it an unctuous sweat, which is carried off by the tides of the Ocean, and thrown up upon the shores of Germany.

Besides the fanciful explanations according to which amber is "produced by the Sun", Pliny cites opinions that are well aware of its origin in tree resin, citing the native Latin name of succinum (sūcinum, from sucus "juice"). In Book 37, section XI of Natural History, Pliny wrote:

Amber is produced from a marrow discharged by trees belonging to the pine genus, like gum from the cherry, and resin from the ordinary pine. It is a liquid at first, which issues forth in considerable quantities, and is gradually hardened [...] Our forefathers, too, were of opinion that it is the juice of a tree, and for this reason gave it the name of "succinum" and one great proof that it is the produce of a tree of the pine genus, is the fact that it emits a pine-like smell when rubbed, and that it burns, when ignited, with the odour and appearance of torch-pine wood.

He also states that amber is also found in Egypt and India, and he even refers to the electrostatic properties of amber, by saying that "in Syria the women make the whorls of their spindles of this substance, and give it the name of harpax [from ἁρπάζω, "to drag"] from the circumstance that it attracts leaves towards it, chaff, and the light fringe of tissues".

The Romans traded for amber from the shores of the southern Baltic at least as far back as the time of Nero. 

Amber has a long history of use in China, with the first written record from 200 BCE. Early in the 19th century, the first reports of amber found in North America came from discoveries in New Jersey along Crosswicks Creek near Trenton, at Camden, and near Woodbury.

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 formed by free radical polymerization of several precursors in the labdane family, for example, communic acid, communol, 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.

Most amber has a hardness between 2.0 and 2.5 on the Mohs scale, a refractive index of 1.5–1.6, a specific gravity between 1.06 and 1.10, and a melting point of 250–300 °C. Heated above 200 °C (392 °F), amber decomposes, yielding an oil of amber, and leaves 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".

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. For this to happen, the resin must be resistant to decay. Many trees produce resin, but in the majority of cases this deposit is broken down by physical and biological processes. Exposure to sunlight, rain, microorganisms, and extreme temperatures tends to disintegrate the resin. For the resin to survive long enough to become amber, it must be resistant to such forces or be produced under conditions that exclude them. Fossil resins from Europe fall into two categories, the Baltic ambers and another that resembles the Agathis group. Fossil resins from the Americas and Africa are closely related to the modern genus Hymenaea, while Baltic ambers are thought to be fossil resins from plants of the family Sciadopityaceae that once lived in north Europe.

Baltic amber with inclusions

The abnormal development of resin in living trees (succinosis) can result in the formation of amber. Impurities are quite often present, especially when the resin has dropped onto the ground, so the material may be useless except for varnish-making. Such impure amber is called firniss. Such inclusion of other substances can cause the amber to have an unexpected color. Pyrites may give a bluish color. Bony amber owes its cloudy opacity to numerous tiny bubbles inside the resin. However, so-called black amber is really a kind of jet. In darkly clouded and even opaque amber, inclusions can be imaged using high-energy, high-contrast, high-resolution X-rays.

Amber from Bitterfeld

Extraction and processing

Distribution and mining

Open cast amber mine "Primorskoje" in Jantarny, Kaliningrad Oblast, Russia
Extracting Baltic amber from Holocene deposits, Gdańsk, Poland

Amber is globally distributed, mainly in rocks of Cretaceous age or younger. Historically, the coast west of Königsberg in Prussia was the world's leading source of amber. The first mentions of amber deposits there date back to the 12th century. Juodkrantė in Lithuania was established in the mid-19th century as a mining town of amber. About 90% of the world's extractable amber is still located in that area, which was transferred to the Russian Soviet Federative Socialist Republic of the USSR in 1946, becoming the Kaliningrad Oblast.

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 is mined through bell pitting, which is dangerous because of the risk of tunnel collapse.

An important source of amber is Kachin State in northern Myanmar, which has been a major source of amber in China for at least 1,800 years. Contemporary mining of this deposit has attracted attention for unsafe working conditions and its role in funding internal conflict in the country. Amber from the Rivne Oblast of Ukraine, referred to as Rivne amber, is mined illegally by organised crime groups, who deforest the surrounding areas and pump water into the sediments to extract the amber, causing severe environmental deterioration.

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 luster is given by polishing 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 that cause the turbidity. Small fragments, formerly thrown away or used only for varnish are now used on a large scale in the formation of "ambroid" 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 gum, as well as by celluloid and even glass. Baltic amber is sometimes colored artificially but also called "true amber".

Appearance

Unique colors of Baltic amber. Polished stones.

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

Yellow amber is a hard fossil resin from evergreen trees, and despite the name it can be translucent, yellow, orange, or brown colored. Known to the Iranians by the Pahlavi compound word kah-ruba (from kah "straw" plus rubay "attract, snatch", referring to its electrical properties), which entered Arabic as kahraba' or kahraba (which later became the Arabic word for electricity, كهرباء kahrabā'), it too was called amber in Europe (Old French and Middle English ambre). Found along the southern shore of the Baltic Sea, yellow amber reached the Middle East and western Europe via trade. Its coastal acquisition may have been one reason yellow amber came to be designated by the same term as ambergris. Moreover, like ambergris, the resin could be burned as an incense. The resin's most popular use was, however, for ornamentation—easily cut and polished, it could be transformed into beautiful jewelry. 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".

Blue amber from Dominican Republic

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 (220 lb) 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. 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. There is also a separate classification 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 utilize regular labdanoid diterpenes (e.g. communic acid, communol, biformenes), while Ic uses enantio labdanoids (ozic acid, ozol, enantio biformenes).

Class Ia includes Succinite (= 'normal' Baltic amber) and Glessite. They have a communic acid base, and 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 from 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 greater than many other fossil resins. Its specific gravity varies from 1.05 to 1.10. It can be distinguished from other ambers via infrared spectroscopy through a specific carbonyl absorption peak. Infrared 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.

Class Ib ambers are based on communic acid; however, they lack succinic acid.

Class Ic is mainly based on enantio-labdatrienonic acids, such as ozic and zanzibaric acids. Its most familiar representative is Dominican amber,. which is mostly transparent and often contains 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

Class IV is something of a catch-all: its ambers are not polymerized, but mainly consist of cedrene-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 main variety is Highgate copalite.

Geological record

Typical amber specimen with a number of indistinct inclusions

The oldest amber recovered dates to the late Carboniferous period (320 million years ago). Its chemical composition makes it difficult to match the amber to its producers – it is most similar to the resins produced by flowering plants; however, the first flowering plants appeared in the Early Cretaceous, about 200 million years after the oldest amber known to date, and they were not common until the Late Cretaceous. Amber becomes abundant long after the Carboniferous, in the Early Cretaceous, when it is found in association with insects. The oldest amber with arthropod inclusions comes from the Late Triassic (late Carnian c. 230 Ma) of Italy, where four microscopic (0.2–0.1 mm) mites, Triasacarus, Ampezzoa, Minyacarus and Cheirolepidoptus, and a poorly preserved nematoceran fly were found in millimetre-sized droplets of amber. The oldest amber with significant numbers of arthropod inclusions comes from Lebanon. This amber, referred to as Lebanese amber, is roughly 125–135 million years old, is considered of high scientific value, providing evidence of some of the oldest sampled ecosystems.

In Lebanon, more than 450 outcrops of Lower Cretaceous amber were discovered by Dany Azar, a Lebanese paleontologist and entomologist. Among these outcrops, 20 have yielded biological inclusions comprising the oldest representatives of several recent families of terrestrial arthropods. Even older Jurassic amber has been found recently in Lebanon as well. Many remarkable insects and spiders were recently discovered in the amber of Jordan including the oldest zorapterans, clerid beetles, umenocoleid roaches, and achiliid planthoppers.

A snail and a few insects trapped within Burmese amber

Burmese amber from the Hukawng Valley in northern Myanmar is the only commercially exploited Cretaceous amber. Uranium–lead dating of zircon crystals associated with the deposit have given an estimated depositional age of approximately 99 million years ago. Over 1,300 species have been described from the amber, with over 300 in 2019 alone.

Baltic amber is found as irregular nodules in marine glauconitic sand, known as blue earth, occurring in Upper Eocene strata of Sambia in Prussia. It appears to have been partly derived from older Eocene deposits 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 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 as well as organisms; the chemical composition of the resin, however, is of limited utility in reconstructing the phylogenetic affinity of the resin producer. Amber sometimes contains animals or plant matter that became caught in the resin as it was secreted. Insects, spiders and even their webs, annelids, frogs, crustaceans, bacteria and amoebae, marine microfossils, wood, flowers and fruit, hair, feathers and other small organisms have been recovered in Cretaceous ambers (deposited c. 130 million years ago). There is even an ammonite Puzosia (Bhimaites) and marine gastropods found in Burmese amber.

Skeleton of the frog Electrorana preserved in mid-Cretaceous Burmese amber.

The preservation of prehistoric organisms in amber forms a key plot point in Michael Crichton's 1990 novel Jurassic Park and the 1993 movie adaptation by Steven Spielberg. In the story, scientists are able to extract the preserved blood of dinosaurs from prehistoric mosquitoes trapped in amber, from which they genetically clone living dinosaurs. Scientifically this is as yet impossible, since no amber with fossilized mosquitoes has ever yielded preserved blood. Amber is, however, conducive to preserving DNA, since it dehydrates and thus stabilizes organisms trapped inside. One projection in 1999 estimated that DNA trapped in amber could last up to 100 million years, far beyond most estimates of around 1 million years in the most ideal conditions, although a later 2013 study was unable to extract DNA from insects trapped in much more recent Holocene copal. In 1938, 12-year-old David Attenborough (brother of Richard who played John Hammond in Jurassic Park) was given a piece of amber containing prehistoric creatures from his adoptive sister; it would be the focus of his 2004 BBC documentary The Amber Time Machine.

Use

Solutrean amber from Altamira in the Muséum de Toulouse

Amber has been used since prehistory (Solutrean) in the manufacture of jewelry and ornaments, and also in folk medicine.

Jewelry

Pendants made of amber. The oval pendant is 52 by 32 mm (2 by 1+1⁄4 in).
Amber necklace from 2000 to 1000 BCE

Amber has been used as jewelry since the Stone Age, from 13,000 years ago. Amber ornaments have been found in Mycenaean tombs and elsewhere across Europe. To this day it is used in the manufacture of smoking and glassblowing mouthpieces. Amber's place in culture and tradition lends it a tourism value; Palanga Amber Museum is dedicated to the fossilized resin.

Historical 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. Traditional Chinese medicine uses amber to "tranquilize the mind".

Amber necklaces are a traditional European remedy for colic or teething pain with purported analgesic properties of succinic acid, although there is no evidence that this is an effective remedy or delivery method. The American Academy of Pediatrics and the FDA have warned strongly against their use, as they present both a choking and a strangulation hazard.

Scent of amber and amber perfumery

In ancient China, it was customary to burn amber during large festivities. If amber is heated under the right conditions, oil of amber is produced, and in past times this was combined carefully with nitric acid to create "artificial musk" – a resin with a peculiar musky odor. Although when burned, amber does give off a characteristic "pinewood" fragrance, modern products, such as perfume, do not normally use actual amber because 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 scent of amber was originally derived from emulating the scent of ambergris and/or the plant resin labdanum, but since sperm whales are endangered, the scent of amber is now largely derived from labdanum. The term "amber" is loosely used to describe a scent that is warm, musky, rich and honey-like, and also somewhat earthy. 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 (a type of tree resin used in incense manufacture), vanilla, Dammara resin and/or synthetic materials.

In Arab Muslim tradition, popular scents include amber, jasmine, musk and oud (agarwood).
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Resin

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Resin
Insect trapped in resin
Cedar of Lebanon cone showing flecks of resin as used in the mummification of Egyptian Pharaohs

In polymer chemistry and materials science, a resin is a solid or highly viscous substance of plant or synthetic origin that is typically convertible into polymers. Resins are usually mixtures of organic compounds. This article focuses mainly on naturally occurring resins.

Plants secrete resins for their protective benefits in response to injury. Resins protect plants from insects and pathogens. Resins confound a wide range of herbivores, insects, and pathogens, while the volatile phenolic compounds may attract benefactors such as parasitoids or predators of the herbivores that attack the plant.

Composition

Most plant resins are composed of terpenes. Specific components are alpha-pinene, beta-pinene, delta-3 carene, and sabinene, the monocyclic terpenes limonene and terpinolene, and smaller amounts of the tricyclic sesquiterpenes, longifolene, caryophyllene, and delta-cadinene. Some resins also contain a high proportion of resin acids. Rosins on the other hand are less volatile and consist of diterpenes among other compounds.

Examples

Examples of plant resins include amber, Balm of Gilead, balsam, Canada balsam, copal from trees of Protium copal and Hymenaea courbaril, dammar gum from trees of the family Dipterocarpaceae, dragon's blood from the dragon trees (Dracaena species), elemi, frankincense from Boswellia sacra, galbanum from Ferula gummosa, gum guaiacum from the lignum vitae trees of the genus Guaiacum, kauri gum from trees of Agathis australis, hashish (Cannabis resin) from Cannabis indica, labdanum from mediterranean species of Cistus, mastic (plant resin) from the mastic tree Pistacia lentiscus, myrrh from shrubs of Commiphora, sandarac resin from Tetraclinis articulata, the national tree of Malta, styrax (a Benzoin resin from various Styrax species) and spinifex resin from Australian grasses.

Amber is fossil resin (also called resinite) from coniferous and other tree species. Copal, kauri gum, dammar and other resins may also be found as subfossil deposits. Subfossil copal can be distinguished from genuine fossil amber because it becomes tacky when a drop of a solvent such as acetone or chloroform is placed on it. African copal and the kauri gum of New Zealand are also procured in a semi-fossil condition.

Rosin

See also: Rosin
Extremely viscous resin extruding from the trunk of a mature Araucaria columnaris.

Rosin is a solidified resin from which the volatile terpenes have been removed by distillation. Typical rosin is a transparent or translucent mass, with a vitreous fracture and a faintly yellow or brown colour, non-odorous or having only a slight turpentine odour and taste. Rosin is insoluble in water, mostly soluble in alcohol, essential oils, ether, and hot fatty oils. Rosin softens and melts when heated and burns with a bright but smoky flame.

Rosin consists of a complex mixture of different substances including organic acids named the resin acids. Related to the terpenes, resin acid is oxidized terpenes. Resin acids dissolve in alkalis to form resin soaps, from which the resin acids are regenerated upon treatment with acids. Examples of resin acids are abietic acid (sylvic acid), C20H30O2, plicatic acid contained in cedar, and pimaric acid, C20H30O2, a constituent of galipot resin. Abietic acid can also be extracted from rosin by means of hot alcohol.

Rosin is obtained from pines and some other plants, mostly conifers. Plant resins are generally produced as stem secretions, but in some Central and South American species of Dalechampia and Clusia they are produced as pollination rewards, and used by some stingless bee species in nest construction. Propolis, consisting largely of resins collected from plants such as poplars and conifers, is used by honey bees to seal small gaps in their hives, while larger gaps are filled with beeswax.

Petroleum- and insect-derived resins

Shellac is an example of an insect-derived resin.

Asphaltite and Utah resin are petroleum bitumens.

History and etymology

The material dripping from an almond tree looks confusingly like resin, but actually is a gum or mucilage, and chemically very different.

Human use of plant resins has a very long history that was documented in ancient Greece by Theophrastus, in ancient Rome by Pliny the Elder, and especially in the resins known as frankincense and myrrh, prized in ancient Egypt. These were highly prized substances, and required as incense in some religious rites.

The word resin comes from French resine, from Latin resina "resin", which either derives from or is a cognate of the Greek ῥητίνη rhētínē "resin of the pine", of unknown earlier origin, though probably non-Indo-European.

The word "resin" has been applied in the modern world to nearly any component of a liquid that will set into a hard lacquer or enamel-like finish. An example is nail polish. Certain "casting resins" and synthetic resins (such as epoxy resin) have also been given the name "resin".

Some naturally-derived resins, when soft, are known as 'oleoresins', and when containing benzoic acid or cinnamic acid they are called balsams. Oleoresins are naturally-occurring mixtures of an oil and a resin; they can be extracted from various plants. Other resinous products in their natural condition are a mix with gum or mucilaginous substances and known as gum resins. Several natural resins are used as ingredients in perfumes, e.g., balsams of Peru and tolu, elemi, styrax, and certain turpentines.

Non-resinous exudates

Other liquid compounds found inside plants or exuded by plants, such as sap, latex, or mucilage, are sometimes confused with resin but are not the same. Saps, in particular, serve a nutritive function that resins do not.

Resin of pine

Uses

Plant resins

Plant resins are valued for the production of varnishes, adhesives, and food glazing agents. They are also prized as raw materials for the synthesis of other organic compounds and provide constituents of incense and perfume. The oldest known use of plant resin comes from the late Middle Stone Age in Southern Africa where it was used as an adhesive for hafting stone tools.

Lumps of dried frankincense resin
Caranna, a hard, brittle, resinous gum from species of Protium

The hard transparent resins, such as the copals, dammars, mastic, and sandarac, are principally used for varnishes and adhesives, while the softer odoriferous oleo-resins (frankincense, elemi, turpentine, copaiba), and gum resins containing essential oils (ammoniacum, asafoetida, gamboge, myrrh, and scammony) are more used for therapeutic purposes, food and incense. The resin of the Aleppo Pine is used to flavour retsina, a Greek resinated wine.

Animal resins

While animal resins are not as common as either plant or synthetic resins some animal resins like lac (obtained from Kerria lacca) are used for applications like sealing wax in India, and lacquerware in Sri Lanka.

Synthetic resins

Main article: Synthetic resin
 
Many materials are produced via the conversion of synthetic resins to solids. Important examples are bisphenol A diglycidyl ether, which is a resin converted to epoxy glue upon the addition of a hardener. Silicones are often prepared from silicone resins via room temperature vulcanization. Alkyd resins are used in paints and varnishes and harden or cure by exposure to oxygen in the air.
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