What is amber? Fossilised resin, prehistoric inclusions and the ancient gem

Chemistry and formation

Amber forms when plant resins are progressively polymerised over geological time. Fresh plant resin is volatile and soluble. Over thousands to millions of years, successive chemical reactions (polymerisation, cross-linking of molecules, loss of volatile terpene components) convert the resin through an intermediate stage called copal and eventually into true amber, which is chemically stable, insoluble in organic solvents, and hard enough to polish. The defining chemical property of Baltic amber (succinite) is the presence of succinic acid (approximately 3-8% by weight), which is the basis of the chemical test that distinguishes Baltic amber from other amber varieties (GIA Gem Reference Guide, 2006, pp. 2-3; Wise, 2016, pp. 369-372).

Physical properties: Mohs hardness 2-2.5 (very soft, scratches easily), specific gravity approximately 1.08 (floats in a saturated salt solution, distinguishing it from glass and most plastic simulants which sink), melting point approximately 250-300°C (burns with a fragrant piney odour), and static electricity generation when rubbed (the ancient Greek word for amber, "elektron," gave us the word electricity) (GIA; Wise, 2016).

Baltic amber: the primary commercial source

Baltic amber (succinite) from the deposits around the Baltic Sea, primarily in Poland (the Kaliningrad region of Russia and the Polish Baltic coast) and the Baltic States, is the world's largest amber deposit by volume and the primary source of commercial amber jewellery. Baltic amber is approximately 34-40 million years old (Eocene epoch) and originated from forests of extinct coniferous trees, possibly related to the araucaria family. The deposits were formed when resin-rich material was carried by ancient rivers and deposited in marine sediments that are now exposed along the Baltic coastline and extracted from mines (GIA; Wise, 2016, pp. 372-375).

Baltic amber colours range from pale yellow through orange, brown, red, and occasionally blue or green. The most common colour is warm honey-yellow to orange. The "butter amber" variety (opaque, creamy yellow) formed when trapped air bubbles in the resin created opacity during fossilisation. Clarity ranges from completely transparent (most valuable for inclusions and visual quality) to opaque.

Dominican blue amber: fluorescence phenomenon

Dominican amber from the Dominican Republic (approximately 15-40 million years old, Miocene epoch) includes a spectacular variety called blue amber that shows a vivid blue to blue-green fluorescence under natural daylight and UV light. The blue colour is not a body colour but a fluorescence effect: the amber body is typically yellow to golden when viewed against a dark background, but appears vivid blue when backlit by daylight or UV due to the presence of polycyclic aromatic hydrocarbons in the resin, which fluoresce intensely in the blue wavelengths. Dominican blue amber commands significant premiums over ordinary amber in collector markets (GIA; Wise, 2016, pp. 375-377).

Burmese Burmite: the palaeontological treasure

Burmese amber (Burmite) from the Hukawng Valley in Kachin State, Myanmar, is approximately 99 million years old, making it among the oldest gem-quality amber known and scientifically the most important commercial amber source. The mid-Cretaceous age (approximately Cenomanian stage) means Burmite preserves organisms from a world before the extinction of non-avian dinosaurs, including insects, spiders, feathers, small vertebrates, and plant material from an ecosystem that no longer exists. Palaeontological publications based on Burmite inclusions appear regularly in high-impact journals including Nature, Science, and Current Biology (GIA; multiple palaeontological publications in Nature 2016-2024).

The commercial Burmite market has significant ethical complications: much of the material is mined in a conflict zone, and some revenues have supported armed groups. Scientific community guidelines now require ethical sourcing documentation for Burmite specimens used in research publications. For collectors purchasing Burmite, provenance documentation and ethical sourcing assurances are important considerations (Nature editorial policies; GIA).

The inclusion premium

Amber's most commercially distinctive quality factor is the presence and quality of biological inclusions. Amber containing well-preserved insects, spiders, plant material, or other organisms commands premiums that can be dramatic: fine specimens with visible insects in good condition regularly sell for hundreds to thousands of dollars regardless of the amber's size, far exceeding equivalent plain amber. Inclusions that represent unusual or scientifically significant organisms, or that show exceptional preservation detail, can achieve far higher prices at specialist auction (GIA; Wise, 2016, pp. 377-380).

The most commercially significant inclusions: insects with intact body structures and legs, spiders with web fragments, feathers (particularly from Burmite), multiple organisms in the same piece, predator-prey interactions frozen at the moment of capture, and organisms representing species not found in the fossil record elsewhere. Certification of significant inclusions by a palaeontologist or natural history institution adds significant provenance value.

Copal vs true amber: the critical distinction

Copal is young, incompletely polymerised plant resin that looks and feels like amber but is chemically distinct and far less stable. Most commercial "amber" from Colombia, Madagascar, East Africa, and the Philippines sold at very low prices is actually copal, typically 100-10,000 years old. Copal dissolves partially in acetone (true amber does not). Copal crackles and crazes over time as it continues to cure. Copal inclusions are real organisms but far more recent than Cretaceous Burmite inclusions, and the preservation is often less complete. The price difference is enormous: true amber commands gem prices; copal is priced as a resin novelty material. Sellers do not always make this distinction clearly (GIA; Wise, 2016, pp. 381-382).

The acetone test distinguishes copal from amber: apply a drop of acetone to an inconspicuous area. Copal becomes sticky and soft; true amber is unaffected. This is a destructive test; only apply to an inconspicuous surface area and test a small amount first.

Amber treatments

Clarification: Cloudy or opaque amber is heated under pressure to remove trapped air bubbles, producing transparent "clarified" amber. Disc-shaped stress fractures called "sun spangles" or "lily pad fractures" are created during clarification and are diagnostic of the treatment. GIA and qualified gemologists identify clarified amber under magnification (GIA; Wise, 2016).

Heat treatment: Some amber is heated to deepen or shift colour (yellow toward orange-red, or to produce a dark "cognac" colour). The treatment is difficult to detect and is commercially widespread.

Pressed or reconstructed amber: Small amber fragments or dust are pressed under heat and pressure to form larger pieces. The resulting material shows a distinctive flow structure under magnification (elongated bubbles, swirling patterns). Pressed amber has lower value than natural amber but is legitimate when properly disclosed (GIA; AGTA treatment codes; Wise, 2016).

Plastic simulants: Modern plastic is the most common amber simulant. Plastic is warmer to the touch and lighter in specific gravity than amber; the saturated salt water test (amber floats, most plastic sinks) is a simple field test. Cellulose acetate and other early plastics are more difficult to distinguish; FTIR spectroscopy is definitive (GIA; Wise, 2016).