Steve Kelland and I are members of the Danbury Mineralogical Society. We attended the Society's January meeting which was a dinner and presentation by Earl Verbeek. It is always good to touch base with Danbury's members. The dinner was excellent and Steve did it again, won a door prize, a pyrite.

Earl Verbeek, geologist at the Sterling Hill Mining Museum and co-author of "Ultraviolet Light and Fluorescent Minerals" spoke to us about energy wave lengths. His slides illustrated the range of energy waves that include the span of wave lengths we humans identify as the different colors of the spectrum. Our span is quite narrow. I found it quite interesting that humans perceive yellow and green the best. This is verified by the way we see the yellow green of fluorescing willemite. Without the tools of our long and short wave ultra violet lamps we would miss a great deal of color in our mineral specimens. As it is with long, medium and short waves we see only a few narrow bands of color. It will be only when advanced UV lamp technology is made more affordable will we be able to enjoy a wider range of color. Earl showed slides of fluorescing minerals from Sterling Hill and Franklin. Many of those intense minerals, willemite, calcite, clinohedrite and esporite have manganese as their activator. It is interesting the manganese can create a different color in each mineral. Earl spoke of some minerals that show a consistent fluorescent color no matter the location, i.e. the whitish-blue of scheelite. Other important activators of fluorescence are the inclusion of the uranyl ion which always gives a yellow green response to many minerals containing uranium. The disulfide ion which gives color to sodalite, wernerite, scapolite and tugtupite is in the yellow, orange and red ranges. The rare earth impurity divalent europium (Eu 2+) is the cause of the deep blue to violet in fluorite. Organic inclusions such as humic acid and petroleum usually give a softer pastel fluorescent response, like we see in the creamy color of the flowstone we collect in Illion, NY or the light root beer color of some fluorites from Illinois.

During the question and answer period naturally I asked about the activators of the various feldspars. I learned that the red fluorescing feldspars, orthoclase, microcline and many of the plagioclase feldspars are activated by Trivalent Iron (Fe3+) and the feldspars that fluoresce intense light blue and blue violet are activated by the impurity, rare earth Europium (Eu).

It was an educational night and we agreed that a trip to Sterling Hill and Franklin was a must in the near future. To listen to Earl explain more about fluorescence would be great.