Many hobbies have a number of sub disciplines.  Rock hounding is no different.  Some people like to look for aesthetic minerals; others like to dabble with small and microscopic minerals called thumbnails and micro mounts; still others look for rare or older specimens collected from mines long since closed and inaccessible.  Today, let's talk about an area of specialization that has been around for a long time and has recently seen resurgence by the rock hounding enthusiast.  That is fluorescent minerals, better know to most as the "glow in the dark" minerals -- those that display vibrant colors.

What makes them glow?  To understand the mechanics of fluorescence, let's revisit our high school science class.  Now, don't panic, we'll keep this simple.  Do you remember the atom?  Remember that it's made up of three main constituents -- protons, neutrons, and electrons?  And, do you remember that neutrons and protons form the center of the atom, called the nucleus, while the electrons orbit around the nucleus somewhat akin to the planets orbiting around the sun?  Let's focus on those orbiting electrons.

The orbital paths occupied by electrons are called electron shells.  Electrons will occupy specific shells, or orbital paths, based on the amount of energy they have.  Electrons in shells near the nucleus have lower levels of energy than those in shells farther away.  Sometimes, when energy is applied from an outside source (like a black light), it will add energy to electrons and they will fly away from their electron shells, similar to a hyperactive kid on too much sugar!  Anyway, when this happens, an electron from a higher shell jumps down to the lower shell to fill the void left by the hyperactive electron.  Since this replacement electron has more energy than it needs, it releases some of it's energy as visible light during the transition, producing the pretty colors you see emitted from the mineral.  Ta-da -- fluorescence!

Rock hounders use ultraviolet lamps to provide the outside energy source that will excite the hyperactive electrons.  Ultraviolet light is divided into long-wave, medium-wave, and short-wave.  Each type of ultraviolet light may produce different colors in the same mineral!  Sometimes only on type of ultraviolet light will work on a mineral, and, in general, short-wave light will work on more minerals than long-wave.  The long-wave source lamps are readily available, and are akin to the black lights you might have hanging next to your favorite velvet poster of Elvis.  Short-wave lamps are generally more expensive.  They are also more dangerous and can damage your skin and eyes if you are not careful.

Minerals that fluoresce may have certain impurities in them, called "activators," that assist in boosting fluorescence.  Activators must be present in the proper concentration ( or quantity) in order for the mineral to fluoresce.  If there is too little or too much of the impurity, the mineral simply won't fluoresce.  Conversely, some impurities, such as iron, tend to inhibit fluorescence.  These impurities are called "quenchers".

One clarification, regarding the terms fluorescence and phosphorescence.  If a mineral stops "glowing" immediately upon removal of the ultraviolet lamp, the mineral is fluorescent.  If, however, it continues to glow for a period of time, then it is phosphorescent.

Minerals and the discovery of fluorescence are historically linked.  The property of fluorescence was discovered by Sir George Stokes in the mid-1800's when he noticed that the mineral fluorite changed colors from green in the shade to blue in the sunlight.  He must have been pretty impressed by that piece of fluorite, because he named this particular property (fluorescence) after it.  Later, when mines started using electric motors and lights, the miners noticed that the initial spark from electric switches caused some of the surrounding minerals to temporarily glow.

In the early 1900's, the New Jersey Zinc mines used ultraviolet lights to help determine ore grades.  Rocks containing high zinc ore glowed a very bright green and rocks with calcite and no zinc ore tended to glow a bright red-orange.  By the way, Franklin, N.J. is one of the most famous fluorescent mineral locations in the world.  (I wonder if the producers of "The Sopranos" knew that?)  During World War II, when tungsten from China was inaccessible, many deposits of scheelite (a tungsten mineral) were found in the west using short-wave ultraviolet light.

So, why the renewed interest in fluorescent minerals?  There are a number of factors.  Ultraviolet lamps are readily available, costing anywhere in the range of $10 to $1,000 or more.  LED ultraviolet lamps are now easily found as well.  Most of the ones used by hobbyists are between $150 and $600.  Fluorescent minerals may cost less than other types of mineral specimens.  Be forewarned, however, that they are getting more expensive, and there are the rather pricey upper-end fluorescents out there.

Many of the traditional mineral collecting locations that have "played out" of the classic mineral specimens are being rediscovered for the variety or type of fluorescent minerals present.  In fact, don't be surprised if you approach an old mine dump, only to find a rather peculiar person lying under a tarp prospecting with an ultraviolet lamp!

OK, so your appetite is whetted and you're ready to go hunting for "them pretty-colored glow in the' dark rocks".  Where can you find them?  First, let me say that there hasn't been a lot of prospecting for fluorescent minerals.  So, if you are aware of some old mine dumps that are safely and legally accessible, they might be worth checking out.  There are some fairly common minerals, like calcite, that tend to fluoresce and phosphoresce.  Calcite is a common gangue, or non-ore, mineral in many of the local deposits.  An area noted for unique fluorescent calcite and another mineral, spurrite, is the Tres Hermanas mountains south of Deming.  The fluorite from Cooke's Peak also tends to fluoresce.  The fluorite from the Gila River area and Burro Mountains doesn't work so well, possibly because coatings of druzy quartz tend to inhibit the penetration of ultraviolet light.  The local chalcedony, a form of quartz, can also fluoresce.  Areas with lots of chalcedony include Round Mountain near Lordsburg and the Mule Creek, NM area.  As always, have fun and be safe out there.

With Christmas around the corner, I thought I'd spend a little time talking about faceted gemstones, with an emphasis on things to look for while shopping for a loved one's gift.  I'm using much of the information for this article from a book, "Jewelry & Gemstones - A Buying Guide," by Antoinette L. Matlins and A.C. Bonanno. Most of the publications by Matlins are very informative, as she writes with the consumer's interest in mind.

Let's begin with a few definitions relative to the anatomy of a faceted stone.  A cut stone can be divided into three areas - the top portion, called the crown; the bottom portion, called the pavilion; and the portion of the stone that separates the top and bottom, called the girdle.  The girdle is generally the widest part of the stone.  The largest facet on the crown, is the table, which is located at the very top of the stone.  The cutlet is the pointed portion on the very bottom of the pavilion.  There are numerous names for the remaining, smaller facets, but we won't dwell upon them for this discussion.


Matlins and Bonanno suggest using six key steps while examining a stone for possible purchase:

1. If possible, examine the stone unmounted.  The stone can be examined more thoroughly and defects spotted more easily when the stone is not set.
2. Make sure the gemstone is clean.  It is hard to look for defects if the stone has a thin layer of dust or body oil on it.  If the jeweler cannot clean it, fog the stone by breathing on it in a fashion similar to cleaning eyeglasses and wiping it with a clean cloth.
3. Hold the stone so that your fingers only touch the girdle.  Jeweler's tweezers are really the preferred method for holding the stone, so, ask your jeweler if he or she has them available for your use.  Be careful, however, that the jeweler will not hold you responsible for any stones that pop out of the tweezers, which commonly happens.
4. View the gem under proper lighting.  Incandescent and fluorescent lighting can adversely affect the general appearance of the gemstone.  If possible, view the stone under natural daylight conditions.  Also, the light source should come from above and behind you, so that the stone will select the light back to your eye.  Don't hold the stone between you and the light source.
5. Rotate the stone and view it from different angles.
6. If you use a jeweler's loupe - basically a glorified magnifying glass - focus it on the surface and then into the interior.  If you don't have a loupe, ask your jeweler for one.

The jeweler's loupe is an extremely useful tool, but a lot of folks don't know how to use one.  Here's how to look like a pro with one.  First, hold the sides of the loupe with your thumb and fore-finger.  Bring the loupe up close to your eye and your thumb against your cheekbone (you don't need to remove your glasses).  Holding the gemstone in your other hand, slowly bring it up toward the loupe.  As it gets closer, it will start to come into focus.  You can adjust the focus for looking at the surface or into the interior of the stone by slightly adjusting the distance of the stone to the loupe. 

If you are using a loupe to identify potential flaws, then you should be using a 10 power loupe - one that will magnify the stone 10 times its normal size.  Keep in mind that higher-power loupes are available, but a gemstone is only considered to have flaws if they are visible under a 10-power loupe.

So, what can a loupe tell you?  For one thing, it can tell you what kind of workmanship went into cutting the stone.  When you look at the stone, imagine slicing it into half from different orientations.  Do the two halves mirror each other?  Does the stone look balanced?  If you are familiar with the different types of cuts, does the stone have the proper number of facets for the cut?  A loupe can also help you spot chips and scratches.  Take time to examine both the table (the large, flat top facet) and the edges of the facet cuts.  Often, people will focus only on the flatter portions of the stone and not enough on the edges where the facets meet.  Also, check the facet edges to see if they have sharp, definitive boundaries.  If the stone is set as a piece of jewelry, check around the prongs or bezels for scratches from setting tools.  Check to see if the stone has been glued on the prongs or bezel.  A properly set stone should not be glued.

A loupe can help you check for bubbles, inclusions, cracks and other flaws.  Most of these types of blemishes will be in the interior of the stone.  Bubbles and inclusions may show up as cloudy areas in the stone.  Cracks tend to show up as linear features.  Finally, a loupe can help you identify certain enhancements made to the stone, such as whether two or more stones have been joined together - something called a doublet and triplet.  Doublets and triplets can usually be identified by looking at the side of the stone for a linear feature, where the two or three stones have been joined together.

While examining the stone, ask questions of the jeweler.  Most jewelers are reputable, and will try to answer your questions to the best of their abilities.  You can ask about carat weight of the stone, the types of cut and how many facets a particular cut should have.  You might also ask if the stone is natural or simulated (i.e., man-made), whether it is a genuine stone or imitation, and whether it has been enhanced (a natural stone that has been treated).

Be wary of marketing labels, as they can be misleading.  For example, there are misnomers like smoky topaz that is not topaz at all - it is smokey quartz.  So, if you are unsure, ask the jeweler if it's the real deal.  If they want to protect their reputation - and most do - they'll be honest with you.

I hope I've armed you with information to assist you with making a more informed decision during the holiday season.  For now, we wish you all a happy holiday season.