Amber is a natural polymer made over many millions of years from the resin of prehistoric pine trees. It is unique and beautiful and can be quite expensive when the pieces are exquisite, or contain rare organic inclusions – insects or plants, which are extinct for a long, long time.
Attempts to counterfeit amber are as old as its history. Colored glass and certain types of hardened resins, such as copal, kaori gum and celluloid were the most common amber imitations. In the recent times, with the development of plastics and synthetic resins, counterfeit or tempered amber became even more difficult to recognize. Moreover, great interest in paleontological objects such as prehistoric insects or plants caused the rise in the production of fake amber inclusions, where common insects are sealed in falsified amber or in copal and sold as genuine prehistoric artifacts.
How to recognize genuine amber? How to be sure that your piece of the “Gold of the North” is authentic and not just a plastic fake? Although there are various tests to help recognize true amber, it is generally not so trivial, especially with the modern methods of “enhancement” of amber. Even the most experienced specialists can be mistaken, as happened to the experts at the British Natural History Museum, who recently discovered that a bee preserved in amber believed to be one of the oldest known examples of this particular species was in fact a fake and probably no more than 150 years old.
The difference between glass and amber is relatively easy to recognize – glass is heavier, colder and harder than amber. On the other side, copal is softer, easier to scratch and it melts at lower temperature.
There are several systematic methods to differentiate true amber from the imitations, each of them based on certain specific property of amber:
1. Floating test.
Specific gravity of amber is only slightly higher than that of water (1.05 - 1.1 g/cm3), which means that it cannot float in fresh water, but does not sink in saturated salty water. The flotation test can be done only on unmounted pieces of amber, without any metal. The salty solution is prepared from about 1 part of salt by weight to 2 parts of water (or when there is still some salt on the bottom after mixing of the solution and after settling for a while). Put your amber piece into the solution and watch it floating. After the floating test, amber should be thoroughly rinsed in clean water and dried.
This floating test trial eliminates glass, heavy phenolic resins and celluloid as amber imitations. However, copal would not be clearly differentiated by this test.
2. Electrostatic charging
Amber has the ability to become electrostatically charged after being vigorously rubbed on cloth (best on wool, felt or silk). This property can be tested with very small pieces of paper, tissue or dust. After rubbing the amber, the pieces become visibly attracted to it from a distance of about ½ inch and tend to cling to the surface. The electrical charge formed on the amber surface is negative.
Vigorous rubbing (on cloth or even on your palm) until the piece of amber gets slightly warm, may cause it to emit weak resinous fragrance (of pine or turpentine) but copal may even begin to soften and the surface may become sticky. A smell of plastic or synthetic chemical indicates fake amber.
Amber is generally tasteless. After washing the specimen in mild soapy water, rinse it thoroughly, and then lick it. There should be no noticeable, specific taste (or only a faint taste), but synthetic resins often have strong, unpleasant, “chemical “taste.
5. The touch test
Amber feels warm to the touch (like plastic), while glass is much colder. It has also a certain “waxy” or “greasy” luster, while glass and “enhanced” amber have a more glossy shine.
Amber has hardness on the Mohs scale between 2 and 3 – approximately 2.5. This means that it cannot be scratched with a fingernail, while copal is softer and can be visibly damaged by a fingernail (it has a hardness of about 1.5). Glass and hard resins also cannot be scratched with a fingernail at all.
7. Scratching test
When scratched with a knife or sharp needle, amber forms small splinters and minuscule chips, while synthetic plastics do not splinter. Glass cannot be easily scratched with a knife. It is best to make a scratch it in a concealed place, for example inside the bead hole.
8. Hot pin test
This is a commonly advised test for amber. The tip of a needle is heated with a lighter or a match. A clever way to protect your fingers when holding the needle is to stick the other end into a piece of cork, carrot etc. – thus forming an ad hoc handle. When the needle becomes red-hot, poke the specimen. In the case of true amber, the needle does not go in too easily and a nice resinous smell is emitted. Softer materials such as plastics or copal melt under the hot needle more easily. Plastics emit acrid or” chemical” smell and may leave a black mark where the needle was inserted.
9. Melting Point
Heating the specimen (or a small fraction of it) can indicate if it is real amber. Amber becomes softer at about 150°C (300°F) and the melting temperature for amber is about 300oC (570°F). However, amber does not really melt (i.e. it does not form a liquid) but rather decomposes above the melting temperature, unlike synthetic resins. Copal melts at lower temperatures and in the conventional way. Amber emits very pleasant piney smell when heated.
Amber is relatively resistant towards solvents and chemicals. On the other hand, almost all plastics are prone to acetone damage, because they dissolve in acetone. Acetone (or acetone-containing fingernail polish remover) can immediately stain the surface and make it tacky and rough. The test can be done by placing a drop of acetone, ether, or 95% ethyl alcohol on the specimen. Real amber should not dissolve or become sticky. While some plastics will not dissolve in the alcohol, they will be dissolved by acetone. Glass will not be affected by any of these solvents, and copal will be damaged by all of them.
Amber (in particular so called blue amber) has the ability to fluoresce under the ultraviolet light (black light). This test is very useful for the blue amber verification, but not so obvious for other types of amber, whose florescence may be sometimes weak and dependent on the particular wavelength of the light. Also, fractured surfaces of amber are more fluorescent than the weathered surfaces.
12. Tests requiring professional equipment
• Refracting index of amber is measured by an instrument called refractometer. Refracting index for amber is between 1,539 and 1,542. For comparison, the refractive index for glass used to produce early imitations of amber, the refractive index is 1,420 - 1,960. A test to check the refractive index can be done by immersing the specimen in a fluid that has similar refracting index and checking if the specimen seems to disappear from view (in a similar way as the ice cube disappears in clear water). Clove oil has a similar refracting index to amber, but it was reported to dull the surface of polished amber. Another suggestion is the use of mineral oil, but still, the oils can be difficult to remove from the pores and cracks, particularly of antique jewelry.
• Polarized light test
In a professional polariscope, optical properties of amber can be determined. With the use of polarizing lens it is possible to illuminate the specimen to obtain a rainbow effect or iridescence in the regions with internal stresses and imperfections. This is a useful test to distinguish amber from synthetic plastics. It can also visualize tempered amber with holes drilled to place fake inclusions etc.
• Infrared spectroscopy
Infrared spectroscopy is a convenient, nondestructive method for precise determination of the molecular structure of the specimen. Not only can it distinguish glass and various plastics form amber, but it also gives a tool to determine the source of amber. In particular, Baltic amber has a specific band at the wavelength of 1200-1260 cm -1. This is attributed to the presence of the succinic acid component, which is characteristic only for the Baltic amber.
AMBROID and PRESSED AMBER
All the above tests can differentiate amber from its imitations made of other materials, such as glass or plastic. There are however methods to “enhance” amber by softening and pressing it in an autoclave under inert gas and under high pressure. This allows the jewelry makers to obtain more uniform, transparent pieces of the desired shape. Sometimes, even the waste particles and small pieces are compressed into a uniform mass of pressed amber, which can be in addition artificially colored. Other “enhancement” involves soaking in hot oils in order to improve transparency.
Physically and chemically - pressed amber is still composed of the original amber matter, and the processing methods may result in higher transparency, less air bubbles and more regular shapes, but unfortunately the original prehistoric value and the beauty of the pressed amber are greatly destroyed as a result of the “enhancement”.
How to distinguish pressed amber from genuine, natural amber?
Here are some tips on how to avoid pressed amber:
Natural amber for jewelry is never cut to a regular shape – it is only tumbled and polished on surface. These tumbled pieces are called “chips” and have various irregular shapes. Holes may be drilled in them to create a necklace. Any amber piece with a regular, unnatural, geometric shape is a pressed piece.
Pressed amber commonly exhibits the so called “sun spangles” or “fish scales” – round fissures that are residues of trapped water or air bubbles which have collapsed under pressure at elevated temperature. Natural amber can exhibit also some fissure-like imperfections, but there are much less and they are less “glistening”.
An important falsification problem in amber relates to the sought-after organic inclusions – insects or botanical pieces, which are “frozen” and preserved in amber for many millions of years. The counterfeits can be prepared by drilling a hole in a natural piece of amber, putting inside a modern insect (sometimes still alive) and sealing it with heated copal. The specimen could be finally filled with matching pieces of amber and heated under pressure in order to achieve seamless sealing. As a result, a beautiful piece with an inclusion can be obtained, which is quite difficult to recognize. It seems that this is a rising problem, with many falsificates being sold on eBay and online.
How to recognize the most obvious fake inclusions in amber?
The genuine insect in amber are never colorful, they are only black. Sometimes in Baltic amber they are covered with some white residue.
The pieces of amber should not contain evident and numerous sun spangles, because it indicates pressed amber.
Too regular shape of the piece is usually suspicious, as well as the lack of imperfections, lack of air bubbles, or the presence of artificially elongated bubbles. Specifically, smooth surface with a glass-like luster and no imperfections on the surface indicate pressed amber. On the other hand, if there are defects on the surface – cracks coming from the inside, rough spots, it suggests natural amber.
Transparent, clear pieces with homogeneous color and centrally positioned insect are probably not genuine.
Lack of any other pieces and inclusions around the insect indicates a suspicious specimen.
The most important factor however is the origin of the amber piece. The best guarantee of the authenticity of the specimen is the reliability of the source. Therefore, suspicious eBay or online “opportunities” should be always carefully verified.