Joined: Sun Oct 16, 2005 12:22 pm Posts: 21602 Location: San Francisco
GIA wrote:
Color Phenomena of Blue Amber Abstract The greenish blue color observed in some amber from the Dominican Republic and Indonesia is actually fluorescence stimulated by ultraviolet (UV) light. A previous study described the color as iridescence over a yellow background, but it is in fact a surface fluorescence. Since this amber can be considered a long-wavelength pass filter with a half-pass wavelength at about 530 nm in its spectral transmittance, it does not transmit either UV or short-wave visible light. As this material completely absorbs light in the UV range and strongly absorbs light in the short-wave visible range, the stimulated blue color is confined exclusively to the surface. The amber from this study also showed the Usambara effect, the phenomenon in which color varies with the path length of light through a sample.
As a general rule I have found phosphorescence is much less rare when you use one of those uv lasers (but I am too scared to use mine much).
Hmmm..We're still talking about amber right? I just had a go with ambers and copals from 6 different countries. Using the following: SW (4w tube), LW (375nm LED), and "UV" laser pointer (actual is 405 nm violet). None of these resins showed any phosphorescence.
This was more my own curiosity, and I think that the Sumatran material may be unique. I will see if I have any Australian amber.. perhaps that one might be phosphorescent?
I found both Aussie and Indonesian ambers in our stone specimen collection. The Australian did not phosphoresce but I was happy to see that the Indonesian did. I received the Australian from Maggie C. Pederson, and the Indonesian from dealer Anil Dholakia.
Definitely so Stephen. Those 405nm laser pointers are fabulous for making stones fluoresce where you wouldn't expect them to. Seems they can cut through a certain layer of the Fe and make some electrons jump up. I have a half dozen of these lasers and we use them in the lab for multiple reasons.
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