UV lights for mineral hunting: shortwave versus longwave

Fluorescent minerals respond differently depending on the UV wavelength, which is why serious collectors often own both a shortwave (around 254nm) and a longwave (around 365nm) light rather than assuming one covers everything. Some minerals only fluoresce well under one or the other, and a mineral can even show a completely different color under each. The classic example most collectors learn early is the willemite and calcite combination from the old Franklin and Sterling Hill zinc mining district in New Jersey, which fluoresces vividly under shortwave and is one of the most famous fluorescent mineral localities in the world. Scheelite is another common one, it typically fluoresces a distinct blue white under shortwave, which is actually used as a real prospecting method for tungsten ore. A genuinely important safety note, never look directly into a shortwave UV bulb or let it shine on unprotected skin for extended periods, shortwave UV can damage eyes and skin similarly to strong sun exposure. Use it in the dark for best results since ambient light washes out weaker fluorescence.