Hi John,
Your led lamp with an output of 395nm is perfect for detecting the
fluorescence of seashells. The red fluorescence visible in some shells
such as the mappas is due to the presence of porphyrins in the outermost
layer of shell material. The porphyrins have a maximum absorption of UV
at around 400nm, the reason your light works well. Other pigments may
contribute some fluorescence, but nothing like the porphyrins. Also, the
actual mineral composition of the shells can produce fluorescence. A UV
light source with a filtered output to reduce the blue and purple color
is best in order to more accurately observe the fluorescence.
http://www.rbridges.com/autofluorescencePlate.jpg
Cheers,
Randy Bridges
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