Amber is a warm material used in jewelry and decorative arts. Its golden-orange appearance and smooth, polishable surface often lead to its classification alongside traditional gems. However, the precise definition of amber remains a point of scientific and commercial confusion. This unique substance, which is not a mineral, challenges standard geological categories. Understanding the science behind its formation clarifies why amber is sought after and how it differs from conventional stones.
Defining Amber: Organic vs. Mineral
The question of whether amber is a gemstone requires looking at the definition of a traditional gem material. A conventional gemstone is defined as a naturally occurring, inorganic solid with a specific chemical composition and a regular, crystalline structure. Amber fails to meet these criteria because it is an organic substance derived from living matter.
Amber is classified by gemologists as an “organic gem material,” a category that also includes pearls, coral, and jet. Its chemical composition is an amorphous mixture of organic compounds, including resins, oils, and hydrocarbons, rather than a fixed mineral formula. Because its structure is amorphous, it lacks the orderly internal arrangement of atoms found in crystalline minerals.
The material is essentially a fossilized tree resin. While it is cut, polished, and valued for adornment like a semi-precious gem, its biological origin means it does not meet the scientific definition of a mineral. This distinction explains why, in a scientific context, amber is not a true mineral, though it is universally accepted and traded as a gem material.
The Fossilization Process
The transformation of soft tree resin into hard amber is a complex process of molecular change over vast periods of geological time. This process begins when resin, exuded by ancient trees, is buried in sediment. Initial hardening occurs as volatile compounds, such as monoterpenoids and sesquiterpenoids, evaporate and leach out.
The next stage is polymerization, where the remaining stable organic compounds bond together to form a highly cross-linked polymer structure. This robust polymerization distinguishes true, ancient amber from younger, semi-fossilized resin known as copal. This transition requires sustained pressure and heat over a minimum of several hundred thousand years, and often millions of years, to complete.
The highly valued Baltic amber, or succinite, contains between 3% and 8% succinic acid within its structure. This acid is a key byproduct of the chemical degradation and cross-linking that occurs during the fossilization of the original resin, which was produced by the extinct Pinus succinifera species. Copal, which is often only thousands of years old, has not undergone this full polymerization and remains chemically less stable, making it susceptible to dissolving in organic solvents.
Identifying Characteristics of True Amber
Genuine amber possesses several physical properties that help distinguish it from imitations like plastic or younger resins. The first is its extremely low density, with a specific gravity ranging from 1.04 to 1.10. This low specific gravity allows amber to sink in fresh water but float when placed in saturated saltwater.
On the Mohs scale of hardness, amber is soft, registering between 2 and 2.5, meaning it can be easily scratched. Despite its softness, it has a resinous luster and a conchoidal fracture pattern, which creates shell-like curves when the material breaks. Another element is its reaction to light, as many types of amber exhibit a pale blue or green glow under ultraviolet light, a phenomenon called fluorescence.
When a genuine piece of amber is heated or scraped vigorously, it releases a faint but distinctive aromatic scent, often described as a warm pine or resinous odor. This characteristic smell is a remnant of the organic compounds and oils that make up the fossilized resin. This combination of low density, specific hardness, and chemical reactions provides a practical way to verify the authenticity of the organic gem.
The Value of Biological Inclusions
The presence of ancient biological material trapped within the fossilized resin is the primary driver of amber’s scientific and monetary value. Inclusions are small organisms, such as insects, spiders, or plant matter, that became encased in the sticky resin before it hardened. The resin’s rapid setting and hardening created an anaerobic environment that preserved the external structures of these organisms in three-dimensional detail.
These fossilized organisms provide unparalleled paleontological data, serving as a snapshot of ancient ecosystems. Scientists can study the morphology of extinct species, trace the evolutionary paths of insects and arachnids, and deduce ancient climate and forest conditions. The cuticle, or external skeleton, survives intact, allowing for detailed comparison with modern species.
The rarity of a piece containing a complete, well-preserved organism significantly increases its market value. Inclusions of vertebrates, such as lizards or feathers, are exceedingly rare, while insects like flies and mosquitoes are more common. The scientific significance of these perfectly preserved specimens elevates amber far beyond the status of a simple decorative stone.