Shades of Green: Earth's Forests -- Amber

Amber isn't always amber-colored; shown here are three pieces of varying shades. Photo by Maya Walters.

The translucent golden gem known as amber is formed from the resin of ancient trees. Amber is found in many areas of the world, and has different characteristics depending on the region, and therefore the kind of tree, that it originated from. The tree sap that eventually formed amber began as a sticky fluid substance, which covered and trapped any small animals, insects or plants that came into contact with it.

Insects are the most common life forms found inside pieces of ancient amber. However, vertebrates including lizards and frogs have also been preserved, and flowers, mushrooms, and feathers have been found as well. Bubbles in pieces of amber hold trapped air and water. Some amber appears cloudy because it contains so many tiny bubbles. When amber has been exposed to air for too long, its color gradually changes from golden to reddish.

Only certain species of plants produce sap that can harden into amber. The most common type of amber is found around the Baltic Sea, but no one knows what kind of prehistoric tree this Baltic amber was produced by.

Amber from different parts of the world can be identified by its unique infrared spectra. Being able to identify the origin of amber pieces helps archaeologists to determine ancient trade routes. The amber trade in Europe began over 5000 years ago, and the substance was widely available in northern Europe. The ancient Greeks and Romans traded wine, oil, salt, silks, tea, bronze, and even gold in exchange for amber from more northern peoples.

"Inclusions" such as insects in pieces of amber greatly increases their value. Photo by Maya Walters.

Some of the oldest known organisms that have been discovered trapped in amber come from the area that is now New Jersey. The oldest known mushroom is one such example. It was found in amber from about 90 million years ago.

In ancient times, amber was so valuable that carrying it any distance could be extremely dangerous. Many merchants who transported amber from northern Europe to Rome were in danger of being robbed or even killed for their valuable cargo. Hidden caches of both rough and polished amber have been discovered buried along ancient trade routes, indicating that some traders tried to hide the treasure before it could be stolen, and, for reasons that can only be guessed at, never returned to collect it.

Just by looking at a piece, it is almost impossible to tell whether it is real amber or younger tree resin. Tests such as whether it floats or picks up a charge of static electricity can help to determine real amber from fake. Photo by Maya Walters.

Amber from the Baltic region was spread across Africa when the Balts traded with the Romans, who then traded with the Egyptians. Some amber was formed in Africa, but its source long remained a mystery. Most of the "amber" pieces that can be bought in many parts of the world are fakes, and sources of true amber in any particular region can be difficult to locate.

Prehistoric peoples carved amber into jewelry as early as 15,000 years ago. Commercial amber trade in Europe probably began around 3500 B.C. It is believed that the presence of amber is responsible for the Bronze Age reaching northern Europe. In these northern areas, there was an abundance of amber, but a lack of metals. The Greeks and Romans wanted amber so badly that they were willing to trade metals to get it, and this was how northern tribes got the materials to make Bronze Age weapons and tools.

Amber is still such a valuable product that manufacturers of false pieces are common. Some fakes are simply made of plastic. Others are made from real amber that is melted together with plastic to form a different substance. Still others are lumps of present-day tree sap, which may look similar to amber but have not gone through the hardening processes that take many millions of years. Pieces of amber with "inclusions" trapped inside are always worth more than plain amber. The fakes that are hardest to detect are made of genuine amber with a hole melted inside, where a present-day insect or other inclusion is placed, then sealed over with melted amber.

Fossils are rarely formed in tropical rainforests because of the climate and soil conditions. This makes the insects, plants, and animals preserved in amber from these regions especially important as records of ancient life forms

The process that forms amber is still a mystery. No one knows what forces cause tree resin to harden into amber, and the substance is impossible to synthesize. It is also uncertain how organisms are preserved so perfectly inside the hardened amber. These entrapped plants and insects (called "inclusions") are probably kept from deteriorating by dehydration. But the tissue of the trapped organisms doesn't shrink, as normally happens with dehydration, and therefore their cells remain in perfect condition. When researchers found bacteria and plant spores preserved within ancient amber, they wondered about the possibility of reviving them. Some bacteria can survive for hundreds of years in a state of resting/waiting, with all their normal metabolic processes halted, and can then revive themselves when conditions become more favorable. People began to wonder if the same thing could happen to bacteria trapped within amber.

On this page: Amber was formed from sap similar to that which can be found on present-day tree trunks. Photos by Maya Walters.

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