[Rockhounds] Alien worlds

[Axel Emmermann]

> 
> Years ago, at a meeting of the Franklin-Ogdensburg Mineralogical Society,
> one of our members showed up with a canister of liquid nitrogen.  The
focus
> of that meeting was to observe how extreme cooling changes the
fluorescence
> of minerals.  And does it ever!  Some minerals (e.g., wulfenite) that show
> only feeble fluorescence at room temperature brighten considerably when
you
> cool them off.

[Axel] A very weak red fluorescing scapolite crystal flared up like a
lighthouse. I think that the spectrum  demonstrates trivalent iron as an
activator. Amazonite supposedly does that too but I ran out of ice before I
got to that. Red fluorescing fluorite from Seilles, Namur, Belgium (see
http://users.telenet.be/axel.emmerman/FiatLux/Halogeniden.html#seilles4
became much brighter than before, with an eerie kind of transparency to the
fluorescence... 


  However, a couple of our test specimens failed to survive
> this procedure.  One broke, and another, rather expensive one had its
> fluorescence permanently impaired.  Liquid nitrogen is great fun if you're
> careful with it, but as Axel has already implied, be sure to use specimens
> that you're prepared to sacrifice.

[Axel] I suffered no casualties... but the again, dry ice falls short 233 °F
of liquid nitrogen.
> 
[Axel] Cheers
[Axel]