Pine Barrens Pebbles

[johnnyb]

Many pebbles found in the Pines are colored when removed from in the ground, but when left on the surface bleach to a chalky white. When sharply struck together in the dark, they briefly glow.
I’ve heard that when struck, some of the electrons in the outer rings of the atoms of the stone’s material are raised to a higher energy level in response to the energy they receive from the impact. Since these energized electrons are in an unstable higher orbit, they quickly fall to their normal orbits, releasing energy in the form of photons as they fall. These photons are seen by us as visible light, illuminating the translucent stone from within.
The stones are mainly silicon dioxide - quartz sand.
But they’re not clear quartz pebbles - the hard-to-find “Cape May diamonds”. Why are they white? How do they differ from clear quartz? Do clear quartz pebbles act in the same way?
Incidentally, quartz is piezo-electric. That is, when bent it creates an electrical voltage, and conversely, if excited by a voltage of a frequency related to the materials physical dimensions, it will vibrate at a specific rate. This phenomenon is used in constructing radio transmitters, sensitive strain gauges, etc. How, and are, the glow and piezo-electric phenomena related?

 

[Sarra]

Many pebbles found in the Pines are colored when removed from in the ground, but when left on the surface bleach to a chalky white. When sharply struck together in the dark, they briefly glow.
I’ve heard that when struck, some of the electrons in the outer rings of the atoms of the stone’s material are raised to a higher energy level in response to the energy they receive from the impact. Since these energized electrons are in an unstable higher orbit, they quickly fall to their normal orbits, releasing energy in the form of photons as they fall. These photons are seen by us as visible light, illuminating the translucent stone from within.
The stones are mainly silicon dioxide - quartz sand.
But they’re not clear quartz pebbles - the hard-to-find “Cape May diamonds”. Why are they white? How do they differ from clear quartz? Do clear quartz pebbles act in the same way?
Incidentally, quartz is piezo-electric. That is, when bent it creates an electrical voltage, and conversely, if excited by a voltage of a frequency related to the materials physical dimensions, it will vibrate at a specific rate. This phenomenon is used in constructing radio transmitters, sensitive strain gauges, etc. How, and are, the glow and piezo-electric phenomena related?

I have no answers for you - however, you may have answered a question I have had for 20 or so years. I was walking through the arboretum at Ocean County College one night and was perplexed by the glowing pebbles I was walking on. I've thought about this on and off for so long and maybe this is what was happening!

 

[Spung-Man]

Johnnyb,

Your pebble observations are interesting. I will have to try this! From the description you are north of the Mullica and looking at Beacon Hill gravels. The Beacon Hill is a “facies” (look it up) of the Cohansey Formation. The quartz and chert pebbles are very old, maybe five to ten million years of age. While pebbles composed of quartz and quartzite are resistant to weathering, cherts and other lithologies can be so deeply weathered that they become soft and crumbly. Upon exposure they rapidly bleach due to the earlier leaching of minerals.

Some Beacon Hill gravels are so rotten they can be crushed by hand. It is a great way to impress the girls on camping trips. It’s a lot like the Lost in Space episode where Dr. Smith tricks Thor into thinking he can squeeze water out of a rock. Just don’t try this south of the Mullica, since the Bridgeton Formation stones are younger and not as far along in weathering.

There is very little Ice Age organic material to radiocarbon date in the Pine Barrens. We were too cold, dry and windy for life to flourish. I use the natural luminescence of windblown quartz and feldspars instead to date Ice Age geologic features. It is a complicated process, but if you really have to know more check out Steve Forman’s site:

http://www.uic.edu/labs/ldrl/​

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I also use Tammy Rittenour:

http://www.usu.edu/geo/luminlab/whatis.html​

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I suspect Sarra’s light show is associated with bioluminescence of microbes and not the internal dynamics of quartz luminescence. The production of “cold light” has long been reported from gem stones. Aristotle and Pliny wrote of luminescent rubies. Diamonds can also glow at night. Highly purified silicon is used as a semiconductor in electronics, so has excellent (and surprising) electrical characteristics.

S-M