Introduction

Fluorescence, and a related phenomena, phosphorescence, are properties of materials that emit visible light when exposed to UltraViolet (UV) light (fluorescence) and continue to emit such light after exposure to UV light (phosphorescence).  That is, phosphorescent materials continue to "glow" even after the UV light is turned off.

Ok, lot of words there.  What does it really mean?  And how does it relate to the black light I remember from college daze?  And what's with this "fluorescent mineral" stuff?

Fluorescence Every Day

For starters, we all experience fluorescence more than we realize.  Ever notice how *bright* white clothing appears in sunlight? The reason is that many  laundry detergents  and bleaches contain trace amounts of fluorescent dyes in them.  Why?  Since there is a component of UV light present in bright sunlight, clothes washed in these detergents  appear, due to the fluorescent affect, to be brighter than clothes not washed with fluorescent soaps

College Daze

OK, now what about black lights?  It's not that easy.  First we must mention that there are two "kinds" or wavelengths of UV light.  There is long-wave and shortwave UV light, and different lamps and UV filters are needed to create each. Black lights are simply long-wave UV lights, with a much larger component of visible light emitted than from the UV lights used to view fluorescent materials such as minerals and stamps.

Stamps?

Ahh  yes, now maybe we are getting closer to fluorescent minerals.  But what's that about postage stamps?  Since the 1960's, many US stamps have been "tagged", that is, treated or coated with a fluorescent material.  The reason is that modern postal equipment senses where the stamp is (and also determines whether there is a stamp at all!) on the envelope, and can thus position the envelope for proper automatic processing.

Fluorescent Minerals

So, based on what you've read above, it must be clear that fluorescent minerals are rocks and crystals that exhibit the properties of fluorescence as described above.  But how do they do it?  Not just any ol' rock will glow, you know. The thing that causes rocks and minerals to glow are impurities, called activators, present in the rocks.  For example, manganese, in very small quantities, will cause calcite to glow red under UV.  Other impurities can cause minerals to glow almost all of the colors of the rainbow.

Where do they Come from?

For now, I will mention 3 of the most famous fluorescent rock producing areas of the world. 

Canada produces a variety of bright orange, yellow and purplelong-wave material, such as hackmanite, wearnerite, and agrellite.

 Cumberland, England and the surrounding area produces the absolute brightest fluorite I have ever seen.  It is perceptibly brighter than other forms of fluorite.All fluorites are primarily long-wave sensitive, though many go both ways. ( The Clay Center, Ohio, fluorite also phosphoresces.)

Finally, the all-star of the fluorescent world, my personal favorite (besides fluorites), the brightest and most captivating minerals that both fluoresce and phosphoresce, the minerals from the Franklin and Sterling Hills mines in New Jersey.  Many of these specimens contain 4 different activators, such as hardystonite (purple), clinohedrite (orange), willemite (green--the most common) and calcite (red).  

Many are simply stunning to look at.

Viewing Fluorescent Minerals

As mentioned there are two effective UV sources, LW and SW.  There are a variety of rocks that glow only under one or the other light, as well as a selection that actually glow under both.  Some materials, in fact, glow different colors under each of the UV lights.

History of Fluorescent Minerals (section under development)