One use for UV light is to identify manganese-bearing glass that
turns purple (or amehtyst or lavender, etc.) under ultra-violet
radiation.  Bottle collectors have used the trick for years and have
several designs for "purpling boxes" using aluminum foil lining to
decrease the necessary time for "turning."

I have used such a device on (otherwise) non-diagnostic bottle shards
to get some sense of a time period.  I have also been criticized on
the grounds that it was a "destructive procedure."  However, it
accomplished its purpose.  Solarized purple glass will revert to its
colorless condition if heated to ca. 450 degrees, but that brings it
dangerously close to its malleable point.

Be aware, however, that concentrated UV light is very damaging to
eyes and should be used only under carefully shielded conditions.
Even a brief dose of dirct light can cause very painful symptoms,
although the damage is usually only temporary.  Prolonged exposure is
quite dangerous.

Bill
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Bill Lockhart
New Mexico State University
Alamogordo, NM
(505) 439-3732