What amber actually is
Amber is an organic mineralloid, fossilized tree resin from extinct conifer and angiosperm species, with no crystal lattice and no stoichiometric formula[IMA][GIA]. The empirical composition averages C₁₀H₁₆O, but the underlying chemistry is a complex polymerized terpenoid mixture rather than a fixed compound. The source resin chemistry varies by parent species: Pinus succinifera dominates Baltic material, the legume Hymenaea protera produces Dominican blue amber, and agathis-type conifers yield Burmite[IGS][USGS]. Amber is the second amorphous gem material in the Gemius catalog alongside opal, the silica-resin pair that sit outside the crystalline majority.
The optical and physical fingerprints are refractive index 1.539–1.545, specific gravity 1.05–1.10, no measurable birefringence, no measurable dispersion in the mineralogical sense, isotropic optic sign, conchoidal fracture, no cleavage, and resinous luster[IGS][GIA]. Mohs hardness 2 to 2.5 places amber as the softest gem material in the catalog. The specific gravity is so low that amber floats in saturated salt water, the classic amber-versus-imitation diagnostic test, recorded by Pliny and still in use today[Gem-A]. Amber also accumulates static charge on friction. The Greek word elektron descends to English electricity through this property[IGS].
Color chemistry
Amber spans Yellow (Gold), Cognac, Cherry, White (Bone), Green, and the apex Blue[GIA]. Yellow (Gold) is the trade default and global volume base, the warm honey hue of unmodified Baltic material[IGS]. Cognac is the saturated brown-orange that develops through partial oxidation, and Cherry is the deep red, almost universally heat-induced from yellow-gold rough through autoclave processing[GIA].
White (Bone) is the unprocessed cream-opaque variety with dispersed micro-bubbles that scatter incident light. Green amber in the trade is most often heat-pressure-treated material. The rare natural-green Dominican variety exists but is uncommon[IGS]. Tone and saturation track together in amber as in most colored material. Very-light and very-dark body tones cannot carry vivid saturation, a chromatic constraint common across colored gemstones.
Blue Dominican amber is the species' apex variety and the most distinctive color chemistry in the catalog. The body color of Dominican blue is in fact yellow-to-pale-yellow under direct illumination. The "blue" reading is fluorescence, not body chromophore[GIA][IGS]. Hydrocarbon constituents in the Hymenaea protera terpenoid matrix absorb ultraviolet wavelengths and re-emit in the blue, so under indirect daylight (rich in UV) or direct UV illumination the stone glows strong blue. Sumatran amber shows the same fluorescence chemistry at weaker intensity. Mexican Chiapas material shows it weaker still. Baltic amber typically fluoresces a weak yellow-green and never reads blue[Gem-A].
Origin science
Amber forms wherever ancient resin-producing forests were buried, slowly polymerized under sediment pressure, and survived geological transport without thermal destruction[USGS]. The five trade origins are separated by deposit age and parent species. Baltic amber is Eocene (40–50 million years), Pinus succinifera-derived, and supplies over eighty percent of global production from the Baltic basin coastal sediments[IGS]. Dominican amber is Miocene (15–20 million years), Hymenaea protera-derived, and the sole source of strong blue fluorescent material[GIA]. Mexican Chiapas amber is also Miocene (22–26 million years), with weaker blue fluorescence than Dominican[USGS].
Burmite, Burmese amber from the Hukawng Valley in Kachin State, is Cretaceous (approximately 99 million years), the geologically oldest commercial amber, and the sole source of the Chameleon / Usambara color shift[Lotus][SSEF]. Sumatran amber is Miocene to Pliocene (geologically the youngest of the five) and shows blue fluorescence comparable to weaker Dominican material[USGS].
Resin chemistry constrains what each origin can produce. Baltic material shows no Blue (its terpenoid fluorescence chemistry does not support it), Burmite runs to the warm-spectrum Cherry, Cognac, and Yellow (Gold) range, the Chameleon color shift appears in Myanmar material alone, and heat treatment holds only on the warm-spectrum colors that respond to autoclave processing without damage[GIA].
Treatment landscape
Amber treatment reduces in practice to two states, Heated and Untreated, but the Heated category covers two distinct autoclave processes[GIA][LMHC]. The first is clarification heating: cloudy Baltic rough containing dispersed micro-bubbles is processed at moderate temperatures and elevated pressure in autoclave vessels, dissolving the bubbles into the resin matrix and converting opaque material into clear or translucent gemstones[IGS]. The second is deliberate sun-spangle creation: thermal stress during controlled heating induces internal disc-shaped fractures that catch light decoratively, a feature commercially desired and intentionally produced[GIA]. Both processes are disclosed under CIBJO and LMHC standards, and heat treatment applies only to the warm-spectrum colors, Cherry, Cognac, and Yellow (Gold), that respond to autoclave processing without damage[CIBJO].
Three further commercial categories sit outside fine-gem grading, and buyers should distinguish them. Pressed amber (ambroid, reconstructed amber, bonded amber) is multiple small pieces fused under heat and pressure into larger forms. The legacy trade sells it as "genuine amber" but it is a composite-stone category analogous to opal doublets, and IAA + Mason Kay-style certification distinguishes it from single-piece material[IAA]. Coatings and dyes alter surface color and wear off over time. Copal-resin fillings obscure cracks. None are fine-amber pricing categories. All require disclosure at point of sale[CIBJO].
Phenomena science
Chameleon / Usambara color shift (Burmite) is a daylight-versus-incandescent hue change documented exclusively in Cretaceous Burmese material[Lotus][SSEF]. The mechanism involves selective absorption by the polymerized terpenoid matrix at wavelengths that differ between the two illumination spectra. This phenomenon appears in Myanmar material alone. The "Usambara" label, borrowed from sapphire trade vocabulary, is the name used here for the effect. "Burmite chameleon effect" is the regional trade term.
Flora-included amber preserves botanical fragments, leaves, flowers, pollen, plant matter, captured in the original resin flow and held intact across geological time[GIA][USGS]. Flora inclusions carry a substantial phenomenon premium reflecting the paleobotanical value layer over the gemological. Insect-included amber preserves arthropod inclusions, insects, spiders, other invertebrates, and is the apex commercial premium tier, valued by both gemmological and paleontological markets[Gem-A]. Buyers should apply diligence: per IGS guidance, perfect-looking insect inclusions warrant suspicion, since arthropods preserved across millions of years are rarely cosmetically pristine, and modern-insect insertion into pressed material is a documented fraud pattern[IGS].
Sun spangles are the decorative internal disc-fracture phenomenon induced by heat treatment, distinct in mechanism from the three natural-inclusion phenomena above[GIA]. The premium is modest. The effect is decoratively desirable but is treatment-derived rather than geologically rare. Sun spangles are recorded as a phenomenon-and-treatment combination at point of sale per CIBJO guidance[CIBJO].
Species identity synthesized from the authoritative sources cited below.