[time-nuts] Old Crystal.

[ed breya]

Haha - interesting pictures. It looks like they really do glow, but I 
doubt it's from anything the crystal element is doing - it and the mount 
structure may just serve as the electrodes for a gas discharge lamp. If 
the envelope is filled with some relatively "inert" gas or mixture, 
instead of vacuum, then you have a discharge lamp. Using say, dry 
nitrogen or krypton (common fillers, I think), you may get the bluish 
color at some conditions. If you excite it with high enough AC voltage 
at limited current, it will strike and run.

I doubt that the crystal would be mechanically damaged unless you could 
somehow apply the excitation at "exactly" the resonant frequency, but 
I'd think it would become no good as a normal crystal anymore, since 
various things could deposit onto or depart from the surface, affecting 
the resonance and Q. If the voltage is high enough that it arcs over and 
ruins the connections, that's another story. The voltage will at least 
be limited by the gas. If the current is allowed to get too high, then 
the whole thing will be shot.

Ed