Amber, prized for its beauty and historical significance, has captivated human interest for millennia. Its warm hues and occasional trapped ancient life forms offer a tangible connection to prehistoric ecosystems. Understanding what amber is made of involves exploring its organic beginnings, the geological processes that transform it, and its resulting characteristics.
The Origin: Ancient Tree Resin
Amber’s journey begins as resin, a distinct viscous secretion produced by certain trees. Unlike sap, which transports water and nutrients, resin serves as a protective mechanism for the tree. It acts as a natural bandage, sealing wounds, and its sticky properties deter insects and pathogens. This protective fluid, typically produced by ancient conifers, would ooze from the bark, sometimes forming large globs on the forest floor. The resin from extinct species like Hymenaea protera is a known source of amber found in regions such as the Dominican Republic.
The Transformation: From Resin to Amber
The transformation from soft tree resin to hard, fossilized amber is a complex geological process. Initially, as resin is exposed to air, volatile compounds evaporate, causing it to harden. Over thousands of years, this hardened resin undergoes polymerization, where its small molecules chemically link to form larger, more stable structures, evolving into an intermediate stage known as copal.
For copal to become true amber, it must be buried under layers of sediment and subjected to sustained pressure and elevated temperatures over millions of years, a process known as diagenesis. This geological pressure and heat drive off remaining volatile terpenes and other compounds, leading to further polymerization and cross-linking. This chemical change results in a stable, inert polymer that is resistant to decay, distinct from fresh resin or copal. The entire process can take anywhere from 2 to 10 million years.
Defining Characteristics: Properties of True Amber
Amber’s unique composition and formation bestow it with several defining characteristics. It is relatively soft, typically 2.0 to 2.5 on the Mohs hardness scale, making it easily carvable but also susceptible to scratching. Its density is low, usually between 1.04 and 1.10, meaning it feels lightweight and, notably, floats in saltwater.
Amber displays a wide spectrum of colors, including yellow, orange, brown, and sometimes rarer greens or blues. These color variations are influenced by microscopic air bubbles, impurities, and the degree of oxidation. Inclusions like ancient insects, plant fragments, or air bubbles are a common feature, trapped in the sticky resin before it fossilized. When rubbed or heated, genuine amber emits a subtle, pine-like or resinous scent.
Authenticity: Identifying Genuine Amber
Distinguishing genuine amber from imitations can be done through simple tests. The saltwater test is a common method: genuine amber floats in a solution of highly salted water (about 7-10 teaspoons of salt per cup of water), while most plastics and glass imitations sink. However, some plastics can also float, so this test is best used with others.
Another indicator is amber’s ability to generate static electricity. Rubbing amber vigorously with a cloth for 20-60 seconds can create a static charge strong enough to attract small pieces of paper or hair. A hot needle test can also be used; if pressed into an inconspicuous spot, genuine amber produces a faint pine-like smell and resists penetration, whereas plastics smell like burning plastic and melt. Visual inspection also helps, as authentic amber often displays slight imperfections, tiny cracks, or irregular shapes, and feels warm to the touch.