Amber is tree resin that hardened and changed chemically over millions of years. It is warm to the touch, light enough to float in salty water, and soft enough to scratch with a steel blade. Most gem amber comes from the Baltic Sea region, with other deposits in the Dominican Republic, Mexico and Myanmar. Pieces holding trapped insects or plant fragments are prized by collectors and scientists.
How amber forms
Many trees release sticky resin when their bark is damaged. It seals the wound and deters insects and fungi. When resin is buried quickly in sediment, often in river deltas or coastal lagoons, it is protected from air and sunlight. Over time the volatile compounds escape and the molecules link into long, stable chains in a process called polymerization. The result is a hard, amorphous solid with no crystal structure.
The process takes a long time. Resin that has partly hardened but remains geologically young is called copal. There is no single age cutoff agreed by everyone, but copal is usually thousands to a few million years old, while gem amber is tens of millions of years old. Older deposits tend to be harder and more resistant to solvents.
Amber is one of the organic gems, a group of materials produced by living things. It sits with jet and petrified wood among the plant-derived members.
Physical properties
Amber has a resinous luster and a hardness of about 2 to 2.5 on the Mohs hardness scale. Its specific gravity of roughly 1.05 to 1.10 is just above that of fresh water, so most amber sinks in tap water but floats in a strong salt solution. The refractive index is about 1.54, and amber is singly refractive, though internal strain can produce patchy effects in a polariscope.
Color ranges from pale yellow through honey and cognac to deep red-brown. Cloudy or opaque amber, sometimes called bone or butterscotch amber, owes its look to countless tiny gas bubbles. Rubbing amber with cloth gives it a static charge that picks up small bits of paper. The ancient Greeks called amber "elektron," and the word "electricity" comes from it.
Baltic amber
Baltic amber, also called succinite, is the most important source for jewelry. It formed in forests that grew across northern Europe roughly 40 to 50 million years ago, during the Eocene epoch. The resin was later washed into marine sediments known as the blue earth layer, which lies along the coast of the Sambia Peninsula in the Kaliningrad region of Russia.
Storms still wash pieces onto beaches in Poland, Lithuania, Russia, Denmark and Germany. Baltic amber contains about 3 to 8 percent succinic acid, a compound used to identify it. The large open-pit operation at Yantarny supplies much of the world's raw material, and the page on how amber is mined describes it. Gdansk in Poland has a long history as a center for amber jewelry.
Dominican and Mexican amber
Amber from the Dominican Republic is younger, usually dated to roughly 15 to 25 million years old. It came from an extinct tree in the genus Hymenaea, a relative of the modern tropical locust tree. Dominican amber tends to be very clear and often contains well-preserved insects, spiders and small plant parts.
A small share of Dominican amber shows strong blue fluorescence. In daylight against a dark background it looks blue on the surface, and under ultraviolet light it glows bright blue. This blue amber is the best-known specialty of the island. Mexican amber from the state of Chiapas is of similar age and origin, and it is also often clear with inclusions.
Burmese amber
Amber from the Hukawng Valley in northern Myanmar, sometimes called burmite, is much older, about 99 million years, from the Cretaceous period. It has been traded for centuries, especially to China, where carved amber was popular. Since the 1990s it has yielded inclusions of great scientific interest, including insects, plants and small vertebrate remains from the age of dinosaurs.
The mining area has been part of an armed conflict, and some scientific organizations have raised ethical concerns about research on amber from the region. Buyers who want to know a piece's origin should ask the seller directly.
Inclusions
Resin is sticky, so it trapped whatever touched it: insects, spiders, seeds, flowers, feathers, pollen and air bubbles. These inclusions can preserve fine detail such as hairs and wing veins. Scientists study them to learn about ancient ecosystems.
Natural inclusions often show signs of struggle, such as a halo of tiny bubbles or a leg pulled away from the body. Fake inclusions, made by setting modern insects in plastic or pressed amber, often look too perfect and lie at an unnatural angle. Large, complete animals in a clear piece deserve close checking.
Treatments and pressed amber
Several treatments are common and widely accepted in the trade, but sellers should disclose them.
- Clarifying: heating amber in oil fills tiny bubbles and makes cloudy amber clear.
- Sun spangles: controlled heating and cooling creates disc-shaped stress fractures that catch the light.
- Darkening: heating in an autoclave darkens the surface to produce red or cognac tones.
- Coating: a thin varnish or colored backing can change the surface color.
- Pressed amber: small fragments are heated and compressed into larger blocks. It is also called reconstructed amber or ambroid, and it often shows flow lines or a grainy texture.
The page on gemstone treatments explains how these methods compare with treatments used on mineral gems.
Imitations and simple tests
Plastics, glass and copal are the main look-alikes. Phenolic resins such as Bakelite, celluloid and polyester resins have all been used to imitate amber.
- Salt water test: amber floats in a strong salt solution. Glass and most plastics sink. Copal floats too, and the test is unsuitable for pieces in metal settings.
- Solvent test: a drop of acetone or alcohol on a hidden spot leaves copal sticky, while amber is unaffected or only dulled. This can damage the surface.
- Hot point test: a heated needle on a hidden spot gives amber a piney, resinous smell. Plastics smell acrid or chemical. This test is destructive.
- Ultraviolet light: Baltic amber usually glows a chalky blue-white or yellowish color. Many plastics react differently.
- Static: rubbed amber attracts small bits of paper, but some plastics do too.
None of these home tests is conclusive. A gem lab can use infrared spectroscopy to tell amber from copal and resin. The guide to identifying gemstones covers why lab confirmation matters.
Care and wear
Amber is easy to scratch and sensitive to heat, solvents and strong light. Keep it away from perfume, hairspray, alcohol and acetone. Do not use ultrasonic or steam cleaners. Clean it with lukewarm water and a little mild soap, then dry it with a soft cloth. Long exposure to sunlight can darken amber and cause fine surface cracks, called crazing. The page on cleaning jewelry safely gives more detail.
Amber suits pendants, earrings and brooches better than rings, which take more knocks. Its light weight makes large beads and pendants comfortable to wear.
Frequently asked questions
How old is amber?
Most gem amber is tens of millions of years old. Baltic amber is roughly 40 to 50 million years old, Dominican amber about 15 to 25 million, and Burmese amber about 99 million.
What is the difference between amber and copal?
Copal is younger resin that has not fully hardened. It is softer, more easily affected by solvents, and tends to craze over time.
Why does some amber look blue?
Some Dominican amber fluoresces blue in daylight and glows strongly under ultraviolet light. The effect comes from fluorescent organic compounds in the resin.
Does real amber float?
Amber floats in strong salt water but usually sinks in fresh water. Copal and some plastics also float, so the test alone cannot prove a piece is amber.