When examining a specimen you should try at least 3 of the following methods detailed here. If the item in question fails any one of the tests, it could well mean the piece is not true amber.
(Test 1) HARDNESS.
Amber has hardness on Moh’s scale in the region of 2 - 3. Using appropriate scratch sticks it should be reasonably straightforward to test the sample under question.
(Test 2) HOT NEEDLE.
Heat a needlepoint in a flame until glowing red and then push the point into the sample for testing. With copal the needle melts the material quicker than amber and omits a light fragrant odour. Amber when tested does not melt as quickly as the copal and omits sooty fumes.
(Test 3) SOLUBILITY.
Copal will dissolve in acetone. This test can be done by dispensing the acetone from an eyedropper onto a clean surface of the test specimen. Place one drop on the surface of the test piece and allow to evaporate, then place a second drop on the same area. Copal will become tacky; amber will remain unaffected by contact with acetone.
(Test 4) UV.
Copal under a short-wave UV light shows hardly any colour change. Amber fluoresces a pale shade of blue.
(Test 5) FRICTION.
Rub the specimen vigorously on a soft cloth. True amber may omit a faint resinous fragrance but copal may actual begin to soften and the surface become sticky. Amber will also become heavily charged with static electricity and will easily pick up small pieces of loose paper.
(Test 6) TASTE.
An antique trader who specialised in amber beads introduced this test to me. She explained that one of the most reliable tests she used was to taste the amber specimen after washing it in mild soapy water and then plain water. Whilst she could make no distinction between copal and amber, she could easily identify plastics and other common substitutes because of their unpleasant or chemical taste. Amber has hardly any taste at all. As a method for identification I have not seen this procedure recorded elsewhere. I can vouch for its effectiveness as a non-destructive method of differentiating between amber and certain other substances often misleadingly labelled amber.
(TEST 7) FLOTATION (Specific Gravity).
Mix 23gms of standard table salt with 200ml of luke warm water. Stir until completely dissolved. Amber should float in such a mixture and some copals together with various plastics sink.
(TEST 8) INCLUSIONS.
Infrequently amber contains Flora or Fauna inclusions. Correctly identifying the trapped Insect or plant should be an excellent indicator of a piece’s authenticity. Most inclusions from ancient amber are of species that are now extinct or significantly changed. Frequently present in Baltic amber are tiny stellate hairs which are release by oak buds during their early growth and some time after,
(TEST 9) POLARISED LIGHT.
Place the suspect piece of ‘amber’ between two sheets of polarising glass or plastic. (Kokin Filter Systems who sell lens accessories for cameras sell such products). Rotate one of the polarising lenses slowly through 360 degrees. In the body of the amber a display of rainbow colours should cycle through the transparent parts of the material. This is due to interference patterns being induced in the polarised light because of the internal strains and stresses within the amber itself. My general experience with this method is that genuine amber and copal always show these colour changes, where as some acrylics, polymers and certain plastic do not. Amber, which has been drilled and then later filled with a contemporary inclusion and resin also, reveals its self via the clear disruption of the colour display. Essentially; an amber piece which does not show interference patterns is unlikely to be true amber.
(TEST 10) KNIFE CUT.
With a sharp knife try to shave off a tiny piece of the amber from an unobtrusive section. Real amber fractures and splinters. plastic and polymers actual cut and tiny shaved pieces can be removed without any splintering of the material.