Amber is tree resin that has been buried for millions of years and polymerised into a stable, hard, fossil material. It is light, warm to the touch, sometimes contains insects, and comes chiefly from the Baltic, with other sources in the Dominican Republic, Myanmar, Mexico and elsewhere. Two things are sold in its place: copal, which is tree resin only thousands to a few million years old and not fully polymerised, and plastic, which is not resin at all. A fourth category — reconstituted or pressed amber — is genuine amber powder fused under heat and pressure.
Properties of amber
Fossil resin, mostly succinic-acid-bearing in Baltic material. SG 1.05–1.10 (barely denser than water), hardness 2–2.5, RI about 1.54, singly refractive with strain, warm to the touch, insulating, and — under long-wave UV — a blue-white to greenish fluorescence, stronger on freshly cut surfaces. Static charge when rubbed (the original "electric" material). Softens at about 150 °C and burns with a resinous, pine-like smell.
Amber versus copal
Copal looks like amber and is often sold as amber (frequently as "Colombian amber" or "young amber"). Differences:
Solvent. A drop of acetone or ether on an inconspicuous spot makes copal tacky or cloudy within seconds; amber is unaffected. This is the classic separation and is mildly destructive; the laboratory uses it only where necessary and on a hidden spot.
UV. Copal usually fluoresces more strongly and whiter than amber; not conclusive alone.
Surface. Copal is softer and often develops a fine network of crazing on the surface with age. Old amber develops a darker oxidised crust.
Inclusions. Modern insects in copal are of living species and are often perfectly preserved; amber inclusions are of extinct species and show the effects of time. This is a specialist assessment.
Infrared spectroscopy separates them definitively, with Baltic amber showing the characteristic "Baltic shoulder" in its spectrum.
Amber versus plastic
Salt-water float. Amber floats in a saturated salt solution (about 1.15 SG); most plastics sink (SG 1.2–1.4), though some polystyrene and foamed plastics float. A useful home test with limits.
UV. Plastics fluoresce in various colours or not at all; the blue-white of amber is characteristic.
Magnification. Amber shows flow lines, natural gas bubbles (often flattened), "sun spangles" (disc-shaped stress fractures, common in heat-clarified amber), and inclusions. Plastic shows round bubbles, uniform colour, and sometimes mould seams.
Static. Rubbed on cloth, amber picks up small paper pieces; many plastics do too, so this is weak evidence.
Hot needle. A heated pin at an inconspicuous point: amber gives a resinous pine smell; plastic gives an acrid chemical smell. Destructive; not used by the laboratory except as last resort.
Weight and feel. Amber is very light and warm; heavy "amber" is glass or filled plastic.
Reconstituted and pressed amber
Small amber fragments heated and pressed into blocks. Genuine amber material, but the structure shows: under magnification, boundaries between fragments, flow patterns of different fragments meeting, flattened bubbles concentrated at boundaries, and sometimes a "blotchy" look. Often also heat-treated to a uniform colour. Should be sold as pressed amber.
Treated amber
Heat clarification — cloudy amber heated in oil to clear it, producing sun spangles. Traditional and common. Heat darkening — to produce "cherry" and "cognac" colours. Green amber — heated and coated; almost all bright green amber is treated. Coating with lacquer. All should be disclosed.
How the laboratory examines amber
SG (salt-water and precise weighing), UV, magnification for flow, bubbles and inclusions, solvent test where needed on a hidden spot, and FTIR where available. Report states: natural amber (and any heating), pressed amber, copal, plastic or other.
Frequently asked questions
Does real amber float?
In saturated salt water, yes. In fresh water it sinks slowly (SG just over 1). Some plastics float in salt water too; use it as one test among several.
Is copal fake amber?
Copal is genuine tree resin, just young. It is a fake only when sold as amber.
Are insects in amber always genuine?
No. Modern insects are set in copal and in plastic and sold as amber inclusions. The host material is tested first; the insect's species is a specialist question.
Is "Baltic amber" a guarantee?
It is a claimed origin, supportable by infrared spectroscopy. Without that, it is a trade description.
Does amber need special care?
It is soft, scratches easily, is damaged by solvents, perfume and heat, and can craze with age. Store separately and wipe with a soft cloth. Organic gems are soft.