Blue Amber

Blue amber is a variety of amber, a fossilized tree resin, that fluoresces blue under ultraviolet light and in sunlight. Dominican Republic amber comes from the extinct Hymenaea protera tree, a legume that produced prolific resin in Caribbean rainforests 25 to 40 million years ago. Resin flowed down trunks, trapped inclusions such as insects and plant matter, was buried in lignite-rich sediments, and polymerized under millions of years of burial heat and pressure. The distinctive blue fluorescence is unique to Dominican amber and occurs because specific anthracene-like hydrocarbon polymers developed under this region's particular burial chemistry. Under direct sunlight or ultraviolet light, the amber absorbs UV photons and re-emits visible blue light through Stokes shift fluorescence. Indonesian blue amber from Sumatra was discovered commercially in the 2010s and shows a similar mechanism, though the parent tree was a dipterocarp species rather than Hymenaea, and the fluorescence is often even stronger.

Blue amber appears yellow to honey-brown in transmitted light but flashes vivid blue when sunlight or UV strikes the surface, the diagnostic optical signature. Specific gravity of 1.05 to 1.10 means it floats in saturated saltwater (about 25 grams salt per 100 milliliters), a classic field test distinguishing amber from plastic imitations (which sink or float differently). Hardness of 2.5 is low enough that a copper penny will scratch it, but it is marginally harder than young copal resin. Resinous luster and warm feel to touch are characteristic. Genuine amber develops static electricity when rubbed briskly and attracts small paper fragments, a property recognized since antiquity (the Greek word 'elektron' means amber). Under 365 nanometer UV lamp, Dominican blue amber glows neon blue; regular amber glows pale yellow-green.