[Rockhounds] colour perception, organic fluorescence, etc

[J. R. Hodel]

Hi Jim,

Years ago a cousin and I were - not lost, just temporarily misplaced, and wound up walking a long way around in the woods of Raleigh county, WV, the Friday after Thanksgiving (late November, into early wintery weather for those not familiar with USA weather patterns) and we got out of the woods onto a country road around 10 pm, after 3 or 4 hours in the woods after dark, in sleety weather.  My cousin was from the city, and pretty upset, but I kept him with me, and we made it out of the woods OK, following the "go downstream" rule.

I noticed in the middle of that walk in nearly pitch dark some glowing fragments on the ground, and called my cousin over.  We picked up some fragments of a stump, and wondered over the glowing dim green light.

There are a lot of "fireflies" in WV too, little bugs that fly and blink in the early evening, one sex is glowworms in the grassy lawns, the other blinks in species-based patterns.  I understand that there's one species of glowworm that is carnivorous, and blinks fake signals of other species to lure in and eat lovelorn fireflies.  So sad!

JR in WV  

--- On Sat, 12/13/08, Jim Daly <sauktown1 at yahoo.com> wrote:
From: Jim Daly <sauktown1 at yahoo.com>
Subject: Re: [Rockhounds] colour perception, organic fluorescence, etc
To: jr50wv at yahoo.com
Date: Saturday, December 13, 2008, 10:41 AM

There's also phosphorescence of organic compounds in the woods at night. Fungi that glow a light blue grow on dead and rotting tree trunks. In the east we called it "foxfire".
This is very likely the same mechanism as the firefly's light and the synthetic equivalentof the Cyalume light sticks.
UV fluorescence is probably the same mechanism- just a different activation wavelength.
Jim Daly

Axel, here in the North American forests we have several woods that fluoresce
under the right stimulation.  Locust (I think the black locust variety native
to the WV forest) glows, as does the shrub sumac.  This isn't the poison
sumac which I think is a western shrub, this is a shrub which bears bright red
fruit clusters with which you can make a pleasent non-intoxicating beverage. 
It glows best in long-wave "black light".  I don't remember which
spectrum locust responds to best.

Do we know what mechanism might cause the fluorescent reaction in organic
materials?

Just wondering, sorry if we're off topic, but it is related to black light,
etc.

Merry Christmas, everyone!

JR





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