Amber is a natural organic compound, a fossil resin mainly from coniferous trees. The main distinctive features are a high degree of decorativeness (sunny color, transparency), lightness, flammability, ability to become electrified by friction, ease of processing for ornamental and jewelry purposes.
Chemical composition of amber
It is dominated by succinoresen C22H36O2 (65%) and succinoabietic acid C25H40O4 (17%). Unlike the resin of modern pine trees, amber is almost completely absent of abietic acid, which during the fossilization process was transformed into succinoresen, bornyl alcohol and polyesters of succinic acid (up to 70%). However, succinic acid (C4H604) is one of the most important diagnostic characteristics of amber. It is present in the products of its dry distillation in an amount of 3-8%.
Physical properties of amber
In terms of hardness and melting point, amber surpasses the best varieties of copal (hardened oleoresin of Quaternary age). Amber dissolves in organic and terpene hydrocarbons.
Amber in its natural occurrence occurs in the form of pieces of various sizes, often reminiscent in shape of the resin secretions of modern coniferous trees:
- surface (stem), resulting from the flow of resin through cracks and all kinds of external damage to the wood;
- intra-trunk, formed under the bark of trees, in cavities between annual rings, in resin hollows and all kinds of pockets and voids.
Among the surface discharges, the most common are drop-shaped deposits, sinter plates, drops, and stalactites with distinct imprints of twigs, bark, and various irregularities in a tree trunk or forest floor. The intra-stem amber secretions are represented by slightly concave plates, thinning towards the edges. There are also secondary forms of resin secretions, the formation of which is associated with the transportation of amber by sea and river waters, glacial, water-glacial, aeolian and other geological reasons, which contributed to mechanical processing and crushing of various pieces into smaller ones. This is the reason for the variety of amber fragments weighing from fractions of a gram to ten or more kilograms. It is believed that the largest amber in the world, called "Burmese Amber", has a mass of 15 kg 250 g, it is stored in the Natural History Museum in London.
The density of amber is 0.97-1.10, which approximately corresponds to the density of sea water. Consequently, amber floats in salt water, but sinks in fresh water. This explains the amazing stability and indestructibility of amber, which has experienced repeated washing and transfer, as well as repeated reburial over tens of millions of years.
Amber melts on a candle flame, and at a temperature of 250-300°C it begins to boil. When heated, it smolders, burns with a white, smoky flame, spreading a pleasant resinous smell (a wonderful distinguishing feature from fakes!). In the Middle Ages, amber was used for fragrant fumigation of rooms. As a result of distillation, dark red amber oil, crystalline succinic acid and succinic rosin are obtained from it.
It is well known that when rubbed, amber becomes electrified and charged with statistical electricity, attracting small objects. This remarkable property of amber was probably first discovered by the ancient Greek philosopher Thales of Miletus (624-547 BC). Subsequently, scientists, having seen bluish sparks when rubbing amber with wool (these micro-discharges of lightning), called them electrons after the Greek name for amber. Amber is a good electrical insulator, its dielectric constant is 2.863. The hardness of amber on the Mohs scale is 2.0-3.0. The absolute hardness of succinite amber, due to the heterogeneity of its structure, varies widely - from 17.66 to 38.40 kg/mm2. It has been established that the hardness of pressed and natural amber is identical.
Amber colors
In general, amber is yellow in color. However, experts distinguish more than 200 color shades, which vary over a very wide range - from almost colorless to yellow, red, brown, white and even black. Opaque varieties are yellow, milky white (bone), pale yellow (ivory), lemon yellow, red-brown, smoky, brown and less commonly black in various shades. Most of the listed varieties can be observed in one piece of amber in the form of a strictly individual, unique color image.
The degree of transparency of amber also varies over a very wide range - from perfectly transparent varieties to opaque black ones. Opaque amber is also called bastard amber. When heated, opaque amber acquires a light golden color. Transparent varieties of amber are pale yellow, greenish, bright red and pale scarlet. Amber is valued not so much for the amazing richness of its sunny-golden color, but for the harmony of purity and transparency.
When exposed to ultraviolet rays, amber glows in different colors. The luster is glassy, resinous, less often waxy, and in bone it is matte. The burrow is uneven, conchoidal and semi-conchoidal, sometimes shell-like; for bone - flat, even.
Properties of amber
Amber is optically isotropic. Its refractive index ranges from 1.538-1.543. The value of the refractive index increases from transparent to opaque varieties, reaching 1.612-1.628 in the surface oxidation crust.
As a rule, in its natural occurrence the surface of amber pieces is covered with a weathering (oxidation) crust of brown, brown-red or dark brown to black color. The color intensity changes from the periphery to the center. The thickness of this crust reaches 1-2, maximum 4 mm. Often when processing amber, incomplete stripping and polishing give the sample an additional intricately delicate color. The weathering crust, of course, is a kind of protection (armor) of amber throughout the long history of its existence. In cases where a whitish coating appears on the polished surface of amber in products or samples (and this is a sign of its aging - oxidation), this layer is removed by mechanical processing (grinding and polishing). What is amber made of? Amber contains small amounts of sulfur, sometimes nitrogen, silicon, metals (Fe, Mg, Mn, Ba, Al, etc.), ash, wood fragments, flower petals, grains of sand, insect inclusions (inclusions), as well as microscopic air bubbles and the voids are usually spherical, less often ellipsoidal, sometimes filled with water droplets.
The air bubbles observed in amber contain 30% oxygen. Amber (and in the past - an “amber drop”) contains moments of life 40 million years ago. Samples of amber with inclusions of representatives of the animal and plant world (one of the most remarkable features of amber): beetles, ants, mosquitoes, butterflies, lizards, pine cones, flowers, leaves and other organic remains are of particular interest to scientists, jewelers and collectors.
The most important positive property of amber as an ornamental and jewelry stone is its viscosity with extremely high decorative properties. It can be sawn well and easily, turned, drilled, ground and polished, and can also be refinished. When boiled in linseed oil, amber becomes discolored due to the oil filling the bubbles in it. This property of amber to absorb liquids is the basis for its coloring with organic dyes added to the oil. As a result of oxidation, amber slowly ages and becomes covered with a thin, slightly cloudy crust.
- Spillers method. Amber crumbs are filled into a steel mold covered with a lid. The container is lowered into a molten paraffin or glycerin mass, where ambroid is obtained under a pressure of 40-50 MPa;
- Trebitsch method. Ground amber is placed in a cylindrical metal container, on which a movable piston presses from above. Amber melted under pressure becomes a fluid mass, which is pushed out through holes in the lower part of the main cylinder.
At the Kaliningrad plant, ambroid is produced under the following conditions: pressure - 0.26 MPa, t - 230-250ºC.
Some features of use
The unique properties of ambroid are in demand not only in the jewelry industry. It is actively used to create various insulating materials in instrument making and electrical engineering. It is used to make devices, utensils, and instruments for medical needs.
Amber is in particular demand for the production of equipment that accompanies the process of blood transfusion and storage. It has ultra-low wettability, inhibits the process of breakdown of red blood cells, hemolysis, being, as it were, a natural preservative.
How to distinguish pressed amber
The physico-chemical properties of amber and ambroid, molded stone are similar, but there are some differences; pressed stones are characterized by:
- inclusions of bubbles of approximately the same shape, differing from chaotic ones in size and distribution in a natural mineral;
- presence of dye clots;
- a type of “patchwork” quilt;
- the structural distribution of material in stone can be spiral-shaped or rectilinear;
- under UV radiation it behaves like an artificial material, transmitting rays and does not reflect like natural stone.
The most important difference between ambroids is the reaction to ether. If you moisten the surface of a natural stone with a drop of ether, it will not change; the pressed stone will become sticky and change color at the site of reaction.
The density and fragility of amber of natural and pressed origin are the same; the quality of refraction of artificial amber is higher.
What do we buy in the store?
Amber- petrified fossil resin, hardened resin of the oldest coniferous trees of the Upper Cretaceous and Paleogene periods. It is used mainly for the manufacture of jewelry and haberdashery, costume jewelry; It is also used in small quantities in pharmaceuticals and perfumery, in the food, chemical and electronics industries.
See also:
STRUCTURE
Does not form crystals, amorphous framework polymer.PROPERTIES
Birefringence, dispersion, and pleochroism are absent. The absorption spectrum cannot be interpreted. Luminescence is bluish-white to yellow-green, in birmite it is blue. Flammable - ignites from the flame of a match. Electrified by friction. Excellent polishing. In the open air, it actively oxidizes (aging), which over time leads to a change in the chemical composition, color, and increased fragility.
MORPHOLOGY
One of the significant criteria of distinction, important for technical qualification, is the fragility number of the fossil resin. It is determined using a microhardness tester, calculated in grams, and varies from values exceeding 200 g (in the case of viscous resins such as succinite) to values of the order of 20-50 g - in the case of brittle resins such as gedanite. Amber is also characterized by a degree of transparency associated with the unequal concentration of microscopic voids in its body. Based on this feature, amber can be called:
“transparent” - without voids, top quality
“cloudy” - translucent, with a cavity density of 600/mm 2
“bastard” - opaque, with a cavity density of 2500/mm 2
“bone” - opaque, reminiscent of ivory in color, with a cavity density of 900,000/mm 2
“foamy” - opaque, resembling sea foam in appearance, with various cavities from the smallest to very large, several mm in size.
Amber is also distinguished by color: there are no fewer shades of amber than there are colors in the spectrum. The reason for such diversity is usually the presence in the body of amber of substances and minerals foreign to the resin. For example, sulfur pyrites or algae give amber a greenish tint. Some minerals can even give amber a special silvery tint.
According to other characteristics, “Overburden amber” is sometimes distinguished - it lies in layers later than the typical bearing layer, samples are distinguished by a thick weathering crust; “Rotten amber” is a variety that is, as it were, transitional from succinite to gedanite (gedano-succinite), sometimes “rotten amber” is mistakenly called gedanite; “Immature amber” - otherwise crantzit.
Inclusions are often found in amber, so-called “inclusions” - arthropods stuck to a drop of resin were covered with new portions of resin, as a result of which the insect died in a quickly solidified mass, which ensured good preservation of the smallest details. Inclusions larger than 10 mm allow the stone to be classified as precious.
ORIGIN
The initial act in the formation of amber was the abundant release of resin from conifers. The reasons for it are very diverse. The main one should be considered a sharp warming of the climate. Pines were also sensitive to external influences. During thunderstorms, hurricanes and similar phenomena, they secreted resin-sap, which had a protective function: quickly hardening, the resin dried on the affected area, protecting the tree from infection through the wound. The bulk of the resin flowed from trees broken during the spring windbreaks. Resin flowed no less abundantly when various forest pests gnawed, pierced and gouged the bark. The trees were forced to heal the wounds inflicted on them. Thick sticky resin formed nodules, clots, clusters, and drops on the trees, which, unable to withstand their own weight, fell to the ground. Sometimes the resin release process was interrupted and resumed after some time, which contributed to the formation of multilayer resin secretions. Insects landed on the resin and stuck to it. Unable to free themselves from the sticky mass, they remained in it forever.
At the second stage, the resin was buried in forest soils. It was accompanied by a number of physicochemical transformations of the resin, the nature of which largely depended on the conditions in which the resin was exposed. In dry, well-aerated soil, the resin was transformed with the participation of oxygen. The resin's stability increased and its hardness increased. In wetlands, in anaerobic conditions, the resin retained its brittleness.
The third stage in the formation of amber is marked by erosion, transfer and deposition of fossil resins into the water basin. Conditions favorable for the emergence and accumulation of amber are associated with the geochemical and hydrodynamic specifics of the basin.
The transformation of resin into amber occurs with the participation of oxygen-containing, potassium-enriched alkaline silt waters, which, when interacting with the resin, contribute to the appearance of succinic acid and its esters in it. At the final stages of this process, not only amber is formed, but also glauconite, a mineral that constantly accompanies amber accumulations, i.e., the transformation of fossil resin into amber and the formation of glauconite occur in the same redox environment. The discovery of glauconite is evidence of a slightly alkaline and slightly reducing environment. The absence of this mineral in the rock is further evidence of intense aeration of sediments.
APPLICATION
Since ancient times, amber has been used to make all kinds of jewelry and household items. Amber was used to make not only wearable jewelry, but also practical items such as cigarette cases, ashtrays, caskets, caskets and even watches. The famous Amber Room occupies a special place in art. Small grains, jewelry production waste and contaminated substandard amber are valuable chemical raw materials for the production of succinic acids, oils and rosin used in the perfume, pharmaceutical and paint and varnish industries.
Amber is also an exceptionally good electrical insulator. Its electrical resistivity is ρ = 10 17 Ohm m, and the dielectric loss tangent tan δ = 0.001. Only fluoroplastic-4 can compete with amber, for which ρ = 10 15 -10 18 Ohm m, tan δ ≤ 0.0001. Amber insulators were used (especially in the 1960s, before the widespread introduction of fluoroplastic) in the ionization chambers of X-ray meters. Typically, fused amber was used - the so-called “ambroid”.
Amber (eng. Amber) - C 10 H 16 O + (H 2 S)
CLASSIFICATION
| Strunz (8th edition) | 9/C.01-10 |
Instructions
Counterfeits that do not have the properties of amber, but successfully imitate it in appearance, are very common. Natural amber can be distinguished by color, shape and degree of transparency. There are three types of amber: (this category includes foam and bone amber), translucent (in this category of amber there are accumulations of voids that give cloudy opacities) and completely transparent. All three categories are counterfeited with equal success.
If natural amber is rubbed with clean wool, it will become electrified and attract pieces of thread, dust, and paper. With a fake one, the effect will be much weaker. Imitation can be determined using a salt solution, but this method is only suitable for unmounted amber. The stone is placed in a salt solution, the fake will sink, and the amber floats on the surface. Authenticity is determined using a magnifying glass; the power must be at least tenfold. Wavy formations that appear during sintering of particles indicate a fake. In this way, you can distinguish amber from various types of polymers and plastics.
It can be much more difficult to distinguish amber from copal, with which they are similar in color and shape. Copal is a fossil resin used in the manufacture of varnishes. When heated, the smell of copal is unpleasant, and amber releases a clove-like aroma. Copal melts more easily and does not become electrified by friction. In essence, it is an unripe resin, and its composition is identical to natural amber, but it is very soft, sometimes even a fingernail can leave a dent on it. If you apply a drop of alcohol to a stone and the surface becomes sticky, it is copal. Acetone stains remain on copal, but not on amber. If copal is processed in an autoclave, it acquires all the properties of natural amber and it is even more difficult to distinguish a fake.
Pressed amber is another common alternative to amber. The product is obtained by processing small pieces of amber with amber flour and adding dyes. At a temperature of 200-250°C and high pressure, the amber crumb melts and becomes a homogeneous mass, retaining almost all the properties of amber. Using a microscope, experts note the changed shape of the bubbles and the general nature of the structure, which now resembles a mosaic or patchwork quilt. This kind of amber, unlike natural amber, softens under the influence of ether - the surface becomes sticky. It is believed that after heating, the special natural sequence and polarity of the molecules is lost, and it is this that is distinguished by its ability to cure many diseases.
Amber is fragile, easily broken by a blow or a fall, but at the same time it is plastic. And this is a very valuable quality, thanks to which the stone lends itself well to mechanical processing. Amber can be sawed, cut, drilled, ground, polished. Amber hardness on the Mohs scale is within from 2 to 3. For comparison: the hardness of gypsum is 2, quartz is 7, and diamond is 10.
Back in the 7th-6th centuries. BC Thales of Miletus knew the ability of amber to become electrified by friction and to attract various small and light objects. Describing the nature of this phenomenon at the beginning of the 17th century, the English scientist W. Gilbert called it electrification, from the Greek name for amber - electron.
According to the Chinese scientist Tao Hongching (452 - 536 AD), only that amber is real, which, if rubbed with your hand and warmed, attracts mustard seeds.
In the first monograph on amber, A. Aurifaber indicated that only processed amber (without oxidized crust), previously rubbed against cloth, leather, etc., has the ability to attract various objects. Moreover, the more amber heats up during friction, the greater the power it has, attracting not only wood shavings, but also iron, silver and gold filings.
Amber does not conduct electricity well, so it was previously used to make insulators. However, when rubbed against woolen fabric, amber becomes electrified and retains negative electrical charges for a long time. The property of attracting pieces of paper, straws, and hair is inherent in all resins, but none of them has such an attractive force as amber. The concept of electricity comes from amber. In ancient Greece they were in use amber spinning wheels and spindles: being electrified by friction, they cleaned the yarn of various impurities.
Amber was even used for amber optics (glasses for glasses, magnifying glasses), made for the first time in 1691 by the famous German master Christian Pershin (S. S. Savkevich).
The development of physical methods in the 17th - 18th centuries made it possible to make interesting observations. So F. Hauksbee in 1705 discovered that amber, when rubbed on wool, gives a bright glow in a vacuum, Moreover, its intensity increases with increasing friction speed. In air this phenomenon was almost not noticed.
In 1816, J.F. John was one of the first to study in detail the physical and chemical properties of amber: degree of transparency, color, morphology, shine, fracture, hardness, fragility, ability to become electrified by friction, smell, taste, powder color, optical properties, specific gravity. The author described the effect of air, water, heat, various reagents, alcohol, alkalis, acids, ether, and oils on amber.
In 1902, a work by V.K. Agafonov appeared, in which the author examines the features of absorption of the ultraviolet region of the spectrum in amber. S.S. Savkevich established that the oxidation of amber occurs more intensely at elevated temperatures, in light and, especially, in ultraviolet rays. The author studied in detail the emission spectra of Baltic amber. Registered luminescence both flat-polished surface and powder with a particle size of about 2 mm.
The results obtained indicate that the luminescence spectrum of Baltic amber is characterized by a wide emission band in the region of 390 - 610 nm with a fuzzy maximum around 510 nm. Thus, the emission spectrum of Baltic amber lies in the spectrum of the electromagnetic field of visible light.
One of the most characteristic chemical features of amber is the presence of succinic acid in the products of its dry distillation.
Thus, the permeability of amber to liquid and gaseous agents was proven.
1.
Until now, not a single solvent is known in which amber would completely dissolve without decomposition. Amber does not dissolve in water. It softens in boiling water (at a temperature of 100 C). Can be partially dissolved in such organic compounds as alcohol (20-25%), ether (18-23%), chloroform (up to 20%), benzene (9.8%), turpentine (25%), linseed oil (18%). ). But it completely disintegrates in hot concentrated nitric acid. In boiling water, amber softens at a temperature of 100˚ C.
2.
One of the special properties is the ability of amber to swell in water. Over a short period of time, the volume of crushed amber placed in water increases by 8%. The ability to absorb a certain volume of water (0.1 - 0.4%) was also noted in transparent amber, which does not contain microscopic voids. Previously it was believed that water penetrates into amber through cracks, but in 1962 Kawasaki proved the fact of water diffusion into amber. Extremely important is the ability of amber to swell in various substances at room temperature, i.e., in fact, ability to absorb various organic and inorganic compounds.
3 . The thermal properties of amber are due to its amorphous structure. When amber is heated above a certain temperature, which is determined by the type of amber, the process of its melting begins, accompanied by chemical reactions with the formation of simple substances. In this case, a weight loss of the starting material from 40 to 30% is observed. Melting of amber is preceded by softening. Already at a temperature of about 50°C, water vapor condenses on the walls of the flask in which amber is located, and at 125 - 130°C, yellow vapor with the smell of amber (aromatic compounds - terpenes and sesquiterpenes) is released. Actually t Thermal destruction of amber begins after 100°C. It is accompanied by weight loss caused by the release of volatile products and gases (CO2, CO, H2, H2S, O2; saturated and unsaturated hydrocarbons, succinic acid, etc.).
According to E. Frakei, amber melts at a temperature of 350 - 380°C. When heated to 1000° C, amber almost completely evaporates, giving off a characteristic smell of sulfur and bitumen. When heated without air access to 140-150°C, amber becomes plastic. These properties are used for heating and pressing amber. When heated, cloudy amber becomes transparent, and during the pressing process, small pieces of amber turn into blanks of any shape. When burned, amber releases vapors with a fragrant odor. In this regard, in the Middle Ages it was used for incense in temples and churches. It was thanks to this property that in ancient Rus' amber was called “sea incense”.
4. Amber under the influence of ultraviolet irradiation luminesces. Transparent amber glows pale blue, cloud, bastard and bone - milky white with a faint bluish tint. Intensity blue The glow depends on the degree of transparency of the amber. The more transparent the amber, the denser the luminescent colors in it. The reasons for the luminescence of amber are the peculiarities of the internal structure and the presence of various impurities.
Research by S.S. Savkevich showed that amber has quite pronounced photoluminescence under the influence of ultraviolet radiation. In addition, amber has triboluminescence (luminescence that occurs when crystalline phosphors are rubbed, crushed or split; caused by electrical discharges occurring between the resulting electrified parts of the crystals - the discharge light causes photoluminescence of the crystalline phosphor). It appears in the form a faint yellowish glow when grinding amber in a mortar in a well-darkened room.
5. Amber does not conduct electricity well, but when rubbed against woolen fabric, it becomes electrified and retains negative electrical charges for a long time, attracting pieces of paper, straws, and hair. This property is inherent in all resins, but none of them has such attractive force like amber. The concept of electricity comes from amber. In ancient Greece, amber spindles and spindles were in use; being electrified by friction, they cleaned the yarn of various impurities. The dielectric constant of amber is 2.863.
6. With prolonged exposure to air, the surface of amber changes. If you break or saw a piece of amber, you can see that its surface is colored more intensely than the central part. In air, amber oxidizes relatively quickly, forming a crust. The thickness of the crust itself largely depends on where the sample is found. Amber extracted from the ground has a thicker crust, it is rough and covered with cracks. Amber exposed to sea waves is much thinner, sometimes barely noticeable, light, transparent, without cracks.
Another important circumstance for understanding the healing properties of amber is the detection using electron paramagnetic resonance in dark brown ambers of paramagnetic centers. The number of paramagnetic centers in these varieties of amber is 100 times greater than in light ambers. In the weathered crust, compared to unaltered amber (in one piece), there are fewer paramagnetic centers. But crust contains weathering compared to unaltered amber more chemical elements, including salts succinic acid.
