Examples of gemstones that can show fluorescence are topaz, opals, rubies, diamonds, citrine, and various colored sapphires. Not every one of these gemstones will fluoresce. Fluorescence is typically a rare occurrence in most kinds of gemstones.
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.
The phenomenon that causes a diamond to glow under black light is called fluorescence. Around 35% of diamonds grown naturally have this component in them, and 95% of them glow a bluish color when exposed to a black light.
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.
The gemstone known as "moonstone" is an alkali feldspar mineral known as anorthoclase or adularia. Some specimens exhibit a beautiful red fluorescence under short wave ultraviolet light as shown in the photograph at right.
The black light test is especially useful if your pearl is undrilled. Under a black light, faux pearls will typically have a milky, bluish-white hue and uniformity in color. Under a black light, authentic pearls in a strand will have different color intensities from pearl to pearl and generally appear tan or yellowish.
U.V. Fluorescence: weak; blue and colorless topaz may show a weak yellow or greenish glow under long wavelength u.v.. Sherry-brown, pink, or golden yellow topaz may show a strong orange-yellow fluorescence under long wavelength u.v. light that is much weaker under short wavelength u.v. light.
Chalcedony is a crystalline variant of silica that comprises fine particles of moganite and quartz. The stone is compact and occurs in many different patterns and colors. It is naturally occurring as a hydrothermal mineral deposit. It glows yellow, green, or white when viewed under black light.
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.
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.
This phenomenon occurs when electrons in certain atoms of a crystallized mineral absorb energy and then release it in small amounts over time. 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.
A pure and natural diamond is known to produce a blue glow when exposed to black light. The impure ones have certain chemical impurities that trigger the glow of other colors like green, white, red, and yellow when diamonds are exposed to ultraviolet light.
Black pearls are formed when that piece of sand gets stuck in the body of a very specific type of oyster, the Tahitian black-lipped Pinctada margaritifera. The interior shell, called the nacre, of most oysters is usually a glossy white or silver but the Tahitian black-lipped oyster features a thick band of black.
Fake diamonds like cubic zirconia do not glow under black light!
Changes in color of amethyst by heat treatment and UV radiation. Amethyst is pleochroic when the polarization of the light is changed from parallel to the c-axis to perpendicular to the c-axis, amethyst changes its color from blue-violet to purple.
Plastics Glow Under Black Light
Other types of plastic are less obvious. Plastic water bottles usually glow blue or violet under ultraviolet light.
Fluorescence is the glow you sometimes see when an object emits visible light. Some diamonds fluoresce when they are exposed to long-wave ultraviolet (UV) rays from sources like the sun. This can cause them to emit a bluish light or more rarely, a yellow or orangy light.
Fluorescence is when a diamond shows a soft glow under ultraviolet (UV) light. This is caused by certain minerals in the diamond. This effect is totally natural, appearing in a third of all diamonds. Most diamonds with fluorescence will glow blue.
In 1735, the French chemist Charles François de Cisternay du Fay determined that lapis lazuli, emerald, and aquamarine were luminescent.
When you go into a dark room and rub two quartz crystals together, you will start to see them glow. This process is called Triboluminescence and it is a flash of light produced from the energy of friction, impact, or breakage.
Black light test:
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.
Both natural and synthetic rubies fluoresce under UV light.