The Star Guide

   "The Universe for Everyone"
Fluorescent Minerals

Is this the newly discovered exoplanet Epsilon Eridani b that orbits the Sun-like star Epsilon Eridani that is 10 light years from Earth???  . . . NO, IT IS NOT.  This is a 2 inch diameter sphere of Sodalite from Greenland that fluoresces a brilliant yellow color under short wave ultraviolet light.  This is just one of the many specimens in the De Lacy Collection that will be displayed on this web page.

Fluorescent and Phosphorescent Minerals

Minerals are able to fluoresce subdued to moderate to even brilliant colors when exposed to ultraviolet light of various wave lengths.  Ultraviolet light is beyond the visible range of the human eye.  It is associated within the violet wave length in the electromagnetic spectrum.  Light between the wave lengths of 320 nanometers to 400 nanometers (nm) is referred to as  long wave ultraviolet light.  This is UVA and is often referred to as the "Black Light" amongst the hobbyist.   UVA can be both a frosted white bulb called "black light" (BL), or the purple bulb, "black light blue" (BLB).   If you have ever been to a dance at night where they have used Black Lights, you may have noticed that white colored cotton shirts will glow a brilliant blueish-white color when exposed to black light or black light blue.  UVB, the mid-range, is 280-320 nm.  Mid-range bulbs are found in 302, 206, and 312 nm.  This range of light produces an interesting fluorescence in some minerals.  Long wave can be found at 350, 368, and 370 nm.  UVC, the short wave range, is below 280 nm.  Shortwave ultraviolet light produces beneficial and harmful exposure to the skin.   Short and mid-range bulbs are always filtered with special short wave filter glass to reduce visible light.  Long wave bulbs can likewise be filtered through long wave filters made of stained glass or exhibitors can use BLB bulbs without filters. 

Light to moderate exposure to UVB assists the body in absorbing vitamin D and also causes the skin to tan.  The UVC, or short wave length of light causes ionization to take place in the skin.  Over exposure can result in painful sunburn and the increased risk of skin cancer.

Fluorescence is a phenomenon that occurs through the process of electron excitation.  The electrons that orbit the nucleus of atoms are known to be in electron shells.  The shells are located at different levels around the nucleus.  The number of electrons in a shell varies with each element.  Electrons in the outer shells carry more energy than the electrons that are closer to the nucleus.

Exposing ultraviolet light to an object may cause an electron in a lower energy state to become excited and move to a higher energy shell.  When the electron(s) drop back to the original shell it (they) release energy in the form of visible light.  Our eyes then detect this visible light and we perceive the fluorescent color.  Some elements will not fluoresce from the wave length of the light source.  Specific atoms that cause fluorescence are known as activators.  The presents of such impurities vary with different minerals.  Minerals such as Calcite fluoresce due to the trace element of Manganese.  Some minerals will "phosphoresce (after flow) when the light source is shut off.  This occurs when the electrons give up the energy at a slower rate when they fall back to their original shells.

The De Lacy Collection

In the late 1940s I saw my first fluorescent minerals at the Natural History Museum at Golden Gate Park in San Francisco.  I was fascinated with the colors visible under ultraviolet.  I then purchased my first short wave ultraviolet (UV) light from Ultraviolet Products in Pasadena, California and started my own collection.  Now I own a Triple Bright Short Wave Display Lamp manufactured by Ultraviolet Systems, Inc.  I have collected minerals throughout California and purchased minerals from other states and countries.

Now the collection.  Enjoy the colors of some of the most remarkable fluorescent minerals in the world.  To see the collection, click on the link at the top of the page for The De Lacy Collection.
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