Triboluminescent Gems

Triboluminescence is an optical phenomenon in which light is generated when certain materials are pulled apart, broken, ripped, scratched, crushed, or rubbed, through the breaking of chemical bonds in the material. The gems below may exhibit Triboluminescence. More information below.

Triboluminescence
The phenomenon of Triboluminescence is not fully understood, but appears to be caused by the separation and reunification of electrical charges. The term comes from the Greek word τριβείν meaning to rub and the Latin word lumen meaning light. There are only a handful of gem type of minerals that may display triboluminescence.

Triboluminescence is often used as a synonym for fractoluminescence, a term sometimes used when referring only to light emitted from fractured crystals. Triboluminescence differs from piezoluminescence in that a piezoluminescent material emits light when it is deformed, as opposed to broken. These are examples of mechanoluminescence, which is luminescence resulting from any mechanical action on a solid.

History
The Uncompahgre Ute Indians of Central Colorado, USA are one of the first documented groups of people in the world credited with the application of mechanoluminescence involving the use of quartz crystals to generate light. The Ute constructed special ceremonial rattles made from buffalo rawhide which they filled with clear quartz crystals collected from the mountains of Colorado and Utah. When the rattles were shaken at night during ceremonies, the friction and mechanical stress of the quartz crystals impacting together produced flashes of light visible through the translucent buffalo hide.

The first recorded observation is attributed to English scholar Francis Bacon when he recorded in his 1620 Novum Organum that "It is well known that all sugar, whether candied or plain, if it be hard, will sparkle when broken or scraped in the dark." The scientist Robert Boyle also reported on some of his work on triboluminescence in 1663. In the late 1790s, sugar production began to produce more refined sugar crystals. These crystals were formed into a large solid cone for transport and sale. This solid cone of sugar had to be broken into usable chunks using a device known as sugar nips. People began to notice that as sugar was "nipped" in low light, tiny bursts of light were visible.

A historically important instance of triboluminscene occurred in Paris in 1675. Astronomer Jean-Felix Picard observed that his barometer was glowing in the dark as he carried it. His barometer consisted of a glass tube that was partially filled with mercury. Whenever the mercury slid down the glass tube, the empty space above the mercury would glow. While investigating this phenomenon, researchers discovered that static electricity could cause low-pressure air to glow. This discovery revealed the possibility of electric lighting.

The science behind Triboluminescence
Materials scientists have not yet arrived at a full understanding of the effect, but the current theory of triboluminescence — based upon crystallographic, spectroscopic, and other experimental evidence — is that upon fracture of asymmetrical materials, charge is separated. When the charges recombine, the electric discharge ionizes the surrounding air, causing a flash of light. Research further suggests that crystals which display triboluminescence must lack symmetry (in order to permit charge separation) and be poor conductors. However, there are substances which break this rule, and which do not possess asymmetry, yet display triboluminescence anyway. It is thought that these materials contain impurities, which confer properties of asymmetry to the substance. Much of the recent work on triboluminescence was done by Linda M. Sweeting at Towson University.

Other examples of Triboluminescence
As mentioned above, triboluminescence can be observed when breaking sugar crystals, especially Wint-O-Green Life Savers, in the dark. Ordinary friction tape (the cloth type - not the shiny electrician's tape) displays a glowing line where the end of the tape is being pulled away from the roll. In 1953, Russian scientists showed that triboluminescence caused by peeling a roll of Scotch Tape in a vacuum can produce energy equivalent to X-rays. In 2008, scientists working at UCLA performed an experiment that showed actual X-rays were produced, which were strong enough to leave an X-ray image of a finger on dental photographic paper; they hoped to use their research to create a new type of x-ray imaging device.