|Blue amber is the rarest of all ambers. When natural light strikes blue amber on a white surface, the light passes through, and is refracted by the white surface. The result is the slight blue hue of blue amber. When the same natural light strikes the amber on a black surface, the light is not refracted by the black surface, but by the actual amber. Hydrocarbons in the blue amber shift the sun's ultraviolet light down in frequency, resulting in the glow of blue amber. This effect is only possible in some specimens of Dominican amber category, in some Mexican ambers from Chiapas and some ambers from Indonesia. Any other amber (such as Baltic amber) will not display this phenomenon, because its original resin is not from the Hymenaea protera tree.|
The polycyclic aromatic hydrocarbons relax to their ground state, absorb high-energy ultraviolet photons and re-emit them as lower-energy visible photons. Less than 1% of all the amber recovered on earth is of blue color.
Blue amber beads from the Dominican Republic