Some minerals glow or fluoresce under ultraviolet (UV) light, such as some shown here. Apatite, quartz, orthoclase feldspar, and muscovite under normal white light and UV light.
The most common fluorescent minerals include calcite, fluorite, and sodalite – though there are many others. Many gemstones (such as diamond, ruby, emerald, amber, and opal) will also fluoresce when exposed to UV light.
Ultraviolet Light: About 30% of diamonds will glow blue under ultraviolet lights such as black light. Fake diamonds, on the other hand, will glow other colors or not at all.
Yooperlite is a name for rocks that consist of a syenite-rich fluorescent sodalite. Sodalite is mineral that fluoresces an orange or yellow color under ultraviolet light.
Calcite, fluorite, and willemite are some of the minerals that do this.
Today, more and more people have a 365nm UV Jade Identification flashlight. Usually, B+C jadeite or filling enhancements will show fluorescence under 365nm ultraviolet light.
Sometimes, tiny amounts of impurities in diamonds can cause them to glow or luminesce under UV light. UV diamond fluorescence occurs in about 35% of colorless (white) diamonds and can be faint or very strong.
Both natural and synthetic rubies fluoresce under UV light.
When you place a real diamond underneath an ultraviolet light, the stone with fluorescence in it will turn blue. But it's important to know that this will only happen with about one-third of all diamonds. A fake diamond, on the other hand, will almost never look blue under a black or UV light.
Typical fluorescent minerals include: aragonite, apatite, calcite, fluorite, powellite, scheelite, sodalite, willemite, and zircon. But almost any mineral can "glow" under UV light with the right conditions. Most pure minerals do not fluoresce (certain minerals such as scheelite are exceptions).
Named in 1821 in honour of Carl Wilhelm Scheele, scheelite is a primary tungsten ore mineral that displays a distinct blue fluorescence. Miners and geologists would often use this to their advantage in the search by using a UV light at night time to locate the tungsten.
Let's take a look at it. Sapphire generally shows no fluorescence to visible light. But that changes if we expose it to short-wave UV. This is most clearly seen in synthetic colorless sapphire, which displays a bluish white ('chalky') emission in the range of 410–420 nm.
Under long-wave UV light, emerald specimens from most localities show very weak florescence or none at all, but some show a strong red. Emeralds from Chivor, Colombia display a very weak red glow. Synthetic emeralds fluoresce dark or strong, dull red.
Using UV Light to Test Gemstones
The types of UV light used in testing are long wave (LWUV) with a principle wavelength of 365nm, and short wave (SWUV) with a principle wavelength of 254nm. Different testing equipment ranges from UV keyrings (typically LWUV) to a UV viewing cabinet.
Because of this, many have an intense red color. In addition, rubies found in marble typically fluoresce red under ultraviolet light—even the ultraviolet light in sunlight. Fluorescence can make a ruby's color even more intense and increase its value. In other locations, rubies can be found in basalt rocks.
Usually fluorescence is blue in color. Less often, a diamond can have yellow or even white fluorescence (other colors too). Diamonds with Strong - or Very Strong - fluorescence can appear quite cloudy, milky or hazy to the naked eye, and emit a prominent and saturated glow in the presence of UV light.
Diamonds that belong to a group called type IIB usually look blue. After they absorb high-energy light like UV light however, type IIB diamonds glow in the dark for a short time. This afterglow refers to the phosphorescence of a diamond which ranges in colour from blue to pink and fiery red, depending on the diamond.
Fluorescence occurs in some diamonds when they are exposed to the concentrated radiation of a UV lamp. Submicroscopic structures in the diamonds cause them to emit a visible light, a fluorescence, which is commonly blue in colour.
Not all specimens of ocean jasper glow in ultraviolet light; however, we have viewed a lot of specimens and most of them fluoresce to some degree under both short wave and long wave ultraviolet light.
Why Does Jadeite Glow? Jadeite glows because it contains uranium. And although it is commonly thought radioactivity is what causes the glow, it's actually the chemistry of uranium that's responsible – not radioactivity.
The most common glowing crystals are well-formed cubic crystals of fluorite, scalenohedral calcite, prismatic apatite, corundum (ruby and sapphire), aragonite, scheelite, and selenite gypsum.