Identification Of Amber

by Manisha G

identification-of-amberThe tests for the identification of fossil resins, and their separation from plastic or other common substitutes, fall into two categories; the profoundly simple and the extremely complex. The normal range of equipment avail­able to the gemologist – refractometer, dichroscope, heavy liquids, etc- has no place in the day-to-day identification of amber. However, most of the equipment that is necessary for testing amber is not expensive. Some of the tests are as under

1.   SURFACE RESISTANCE TO SOLVENTS TEST

The surface of a piece of copal (kauri, dammar, etc.) will be dissolved when a drop of ether is placed on it for period of one minute (choose an inconspicuous spot). The surface becomes sticky and an imprint of a figure can often be made where the ether is in contact with the resin. A strong aromatic smell is usually released and, on drying, a white chalky mark may be left behind. This test is useful for distinguishing between amber and more recent natural resins. It is somewhat destructive to old carved copals (of which there are surprising number), and must therefore be carried out with caution on these pieces) Repolishing of the tested portion of the surface will usually be necessary and may spoil the overall patina. Amber is unaffected by ether.l

On a basic level, perfumes and hair sprays will damage the surface of amber jewellery over a period of time. The surface will become dull and opaque, and the items will need repolishing.

2.   SPECIFIC GRAVITY TEST

SG = 1.08. In concentrated salt water Amber floats.

3.    SPLINTERS UNDER KNIFE

A most useful test for amber, providing that care is used in its application, is to apply the blade of a knife to an in­conspicuous spot and test for peeling effect. Amber, pressed amber and the copal resins break away in powdery splinters or chips. Glass is not touched unless a great deal of pressure be applied. Bakelite is resistant to the blade but will tend to peel off in rather large chips, while the other plastics peel easily.

4.    HOT POINT TEST

Amber and copal will burn with an aromatic smell: Bakelite and casein will only char, the first tending to give off a carbolic smell and the second that of burnt milk. Celluloid will burn readily, while the safety celluloid (cel­lulose acetate resin) will burn less readily and give off a vinegar smell. Amber gives off smell of succinic acid with hot point test.

5.    INCLUSIONS

A.   ORGANIC INCLUSIONS

Organic remains of insect or plant life that have been caught up in once-liquid resin are termed inclusions. The world of inclusions is one of advanced science, and the gemmologist is only expected to maintain a questioning mind with the 10x lens. However, it is to be hoped that if some­thing ususual does come his or her way it will be passed on to the palaeobotanist or palaeoentomologist to make specialist analysis.

Inclusions in amber vary in size from those visible with enlargement to those about 4cm in length. Most are a matter of millimetres and if an inclusion of a present day sized moth of beetle is found, the piece if often a modern resin. Care must be taken with some of the lesser known nineteenth- century collections, for example the Perowne Collection of Ambers, Sedgwick Museum, Cambridge, Britain, where many of the inclusions described in amber during the past century are in fact inclusions in copal, or non-fossil resins.

The inclusions, both botanical and entomological, found in fossil resins have not shrunk to their small size; it is simply that the larger species managed to extricate themselves from the sticky resin before it overwhelmed them. Under a microscope there is often evidence of quite a struggle from insects before their death; indeed, this can often be useful evidence when querying th authenticity of the inclusion.

B.  INORGANIC INCLUSIONS

Care must be taken with the cursory identification of inclusions so that inorganic inclusions like bubbles, especially those subsequently filled with metallic matter, or water, are not mistaken for plant or animal debris. Inorganic inclusions have an interest in their own right but to date have not been studied extensively, with a few exceptions. There is no such inclusion as the ‘lily-pad’ or ‘nsturtium leaf – these are simply discoidal stress rings, caused by heating the resin either naturally or as part of a production process.

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