Be sure to see 3-D images of hardystonite  & clinohedrite fluorescing!

Introduction to Franklin fluorescence

Franklin fluorescence

	Calcite (red) and willemite (green) glowing under shortwave ultraviolet light. Franklin, NJ. Width 20 cm. (images may take a few seconds to appear)

One of the most remarkable features of many Franklin-Sterling minerals is their fluorescence under ultraviolet light.

More than 80 mineral species found at Franklin-Sterling glow in various colors—a world's record.

Seeing is believing

Watch the photo on the right change as UV light is applied. Then, click on any of the 'photo pages' at left to see more Franklin minerals luminesce.

This site contains many photographs of such specimens, as they appear in a darkened room when exposed to short-wave ultraviolet light. Take a look around!

What is fluorescence?

Fluorescence is a physical process where electromagnetic radiation (light) of one wavelength, striking a particular substance, causes an emission of electromagnetic radiation (light) of another, longer, wavelength.

In the case of interest to us here, the incident electromagnetic radiation is in the ultraviolet range, and the emitted electromagnetic radiation is in the visible.

An extraordinary number of fluorescent minerals are found at Franklin and Sterling Hill. Most of these, including the most brilliant ones, fluoresce best under short-wave ultraviolet radiation.

Electromagnetic spectrum. Shorter wavelengths (higher frequency) are to the right. Note that only in the portion marked 'visible light' are any colors apparent to our eyes.

Such radiation (254 nm) is typically produced by a mercury-vapor lamp. The short-wave ultraviolet light emitted by these lamps is invisible, but the fluorescent response from Franklin-Sterling Hill fluorescent specimens can be brilliant.

Many photographs of fluorescent minerals can be seen on this site listed under 'photo pages' and 'descriptions' on the left.

	Diagram of the fluorescence process. (1) An electron orbiting around an atom's nucleus in its normal state. An incident light beam (2), interacts with the orbiting electron, and the electron (3) is sent to a higher energy orbital state (4). The electron then returns (5) to its original, or 'ground' state (6), and in the process releases a correspondingly lower frequency ray of light (7). Courtesy of Steven Haddock, Ph.D.
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