Green amber is a captivating fossilized tree resin, distinguished by its unique coloration that ranges from a pale olive to a deep forest green. Like all amber, it began as a sticky, aromatic secretion from ancient trees millions of years ago, but its particular hue makes it a rare and highly sought-after variant. The origin of this distinct color is complex, arising from specific geological conditions and sophisticated human-applied techniques. Understanding green amber requires examining both the ancient, natural processes and the modern, commercial enhancements responsible for its vibrant appearance.
Formation and Definition of Amber
Amber is defined as fossilized tree resin that has undergone polymerization and hardening over a minimum of two to ten million years. The original resin, exuded by ancient conifers, acted as a protective mechanism against injury and infection. This soft, viscous substance then had to be buried under layers of sediment, protected from oxygen and subjected to immense pressure and geological heat.
Over this vast span of time, volatile organic compounds in the resin evaporated, and the remaining material chemically cross-linked in a process called polymerization. This transformation turns sub-fossil resin, known as copal, into true amber—a hard, durable, and chemically stable material. Baltic amber, or succinite, for example, is primarily sourced from the fossilized resin of an extinct pine species, Pinus succinifera, dating back about 40 to 50 million years. Green amber is simply any specimen of this ancient fossilized resin that exhibits a greenish tint.
The Natural Processes Behind the Green Hue
Naturally occurring green amber is an exceptionally rare find, making up a very small percentage of all mined amber. The coloration results from the interaction of light with microscopic inclusions or external compounds absorbed during fossilization, rather than a single pigment. One primary natural mechanism involves the incorporation of trace elements or organic matter into the resin while it was still soft.
In some cases, the resin fell into sediments rich with plant material, allowing organic compounds like chlorophyll to infuse the material as it hardened. This subtle absorption creates a faint, often cloudy or olive-green tint within the amber matrix. Furthermore, certain geological environments, particularly those yielding Dominican amber, can introduce minerals such as glauconite or chlorite into the resin. These mineral inclusions scatter light in a way that the human eye perceives as green.
Naturally green amber, particularly that found in the Dominican Republic, can also exhibit strong fluorescence under ultraviolet light. This optical property is caused by polycyclic aromatic hydrocarbons within the resin structure, which absorb UV light and re-emit it as a visible, bluish or greenish glow. This geological and chemical interaction ensures that genuine natural green amber typically displays a non-uniform, subtle coloration, highly prized for its rarity.
Thermal Treatment and Color Enhancement
The vast majority of brilliant green amber in the commercial market results from human intervention through thermal and pressure treatments. This process begins with common, often cloudy or opaque, yellow or clear amber subjected to carefully controlled conditions to artificially induce the green color. The process involves placing raw amber pieces into a high-pressure chamber, known as an autoclave, with an inert gas like nitrogen or argon, or sometimes specific oils.
The chamber is then heated to temperatures ranging between 180°C and 200°C under high pressure. This intense heat clarifies the internal structure of the amber by dissolving the thousands of tiny gas bubbles responsible for its original cloudiness. Subsequent rapid cooling causes internal stress fractures to form, known as “sun spangles.” These disc-shaped fractures act as tiny prisms, scattering light to create a perceived green sparkle.
The green coloration itself is often achieved by roasting the surface of the amber, particularly the weathered outer layer, in an oxygen-free environment, or by applying a nitrogen-based treatment. This process causes a shallow oxidation layer on the surface. When viewed through the newly clarified, yellowish body of the amber, this layer creates an optical illusion of a deep, uniform green. This treated material provides a rich, transparent color rarely achieved in nature.
Distinguishing Natural from Treated Samples
For the consumer, differentiating between naturally colored and heat-treated green amber relies on specific visual and scientific cues. Natural green amber typically presents with a softer, more muted tone, often resembling olive or moss green, and frequently has an opaque or cloudy appearance. The color distribution tends to be uneven, reflecting the organic and mineral inclusions that caused the tint.
In contrast, treated green amber is usually characterized by a vibrant, uniform, and highly transparent color, often accompanied by numerous “sun spangles.” These small, circular, lily-pad-like fractures are a near-certain indicator of heat and pressure treatment. Another reliable testing method uses shortwave ultraviolet light. While both natural and treated amber can fluoresce, natural green Dominican amber often exhibits a much stronger, sometimes intense, bluish-green glow compared to its treated counterpart. Because the human-enhanced process yields a more dramatic and commercially appealing color, treated green amber is far more common in jewelry than the subtle natural variety.