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About Minerals

UV Light and Fluorescent Minerals

The hobby of collecting and enjoying fluorescent minerals is of recent origin. It really got its birth as the result of the search for strategic mineral ores during and after World War II. Thomas Warren founded UV Products company just as Roosevelt was elected in 1932. He had to petition Congress to allow him to continue to buy ample supplies of copper and steel during WW II so he could produce UV bulbs. They were being used to find deposits of Sheelite, a much needed tungsten mineral.

HardystoniteNow let's take a look at UV Light. We have invisible light at both ends of the visible light spectrum. Our visible light lies in the range of 400nm to 700nm, a nm (nanometer) being 1/1,000,000 of a meter. Violet light being at 400nm and Red light being at 700nm. Infrared light lies beyond 700nm, and while invisible, it is sensed as heat. UV or ultraviolet light lies below 400nm, and while invisible, it is the spectrum of light that gives you sunburn. The UV light useful for mineral collections is between 400nm and 250nm. Longwave UV light, also known as black light lies between 400nm and 350nm. Short wave UV light lies between 300nm and 250nm. While both types of UV light are produced by the sun, only Longwave UV light reaches the Earth, with Short wave UV light being absorbed by the atmosphere. The middle range of UV light, especially around 310nm is the sunburn causing light, it also activates Vitamin D and provides bactericidal action.

Most fluorescent minerals fluoresce most brilliantly in shortwave UV light. Shortwave UV light can be harmful to the eyes with anything beyond limited exposure. The shortwave bulb uses a vacuum tube filed with Argon gas to which a small drop of Mercury has been added. The tube must be made of high silica glass or quartz since sw UV light will not pass through most glass or plastic. A 40W incandescent light bulb would be considered dim, where at 15W sw UV light is capable of lighting up a whole mineral display.

Willemite/Calcite/Clourite/AragoniteMinerals that fluoresce have an atomic structure that will respond to UV light. Most solids, and nearly all minerals are arranged in a precise 3 dimensional array. As minerals crystallize on earth, it is common for stray elements to become incorporated as impurities. These are important because they cause a mineral that would not normally fluoresce to fluoresce. Such an impurity is called an activator. These impurities allow electrons in the atoms of the mineral to absorb energy from the UV light. The electrons then jump to a higher orbit. When they give up their energy and fall back to the lower orbit, they give off light and a minute amount of heat. This light is what we see as fluorescence. Common activators are Tungstate; Molybdate; and Uranyl ions. Mercury, Lead, Boron, Titanium; Manganese; and Chromium to mention a few.

Quenchers of fluorescent light are Iron; Nickel; Copper; and Cobalt. The presence of these elements in even minute amounts can reduce or eliminate fluoresence in minerals. While in a few rare exceptions, like Copper Iodide, which is fully 1/3 copper, it will fluoresce brilliant red in longwave UV light. So it never hurts to give a specimen a try.

Common mineral groups likely to fluoresce are Sheelite; Willemite; Apatites; Calcite; Dolomite; Aragonite; Uranium Group; Zinc minerals; and Lead minerals. Gemstones that fluoresce are Amber; occasionally Beryl; Corundum, ie. Ruby; Diamond; Spinel; Topaz; Zircon; Chalcedony; Opal; Quartz.

Locations where fluorescent minerals can be found are Franklin and Sterling New Jersey with world renowned deposits. Oregon and Wyoming thunder egg deposits; Opal deposits in Nevada; Sheelite deposits in Arizona; Fluorite from Ohio; Uranium from New Jersey; and minerals found around hot springs in Texas and California.

When cleaning minerals, be sure the soap used to clean them does not fluoresce. Also be sure the glue used to display fluoresce minerals does not fluoresce.

I hope this might open up a new area of mineral interest for you.