By Linda Weiford, WSU News
PULLMAN, Wash.- The small hand and nose prints left on the viewing glass at Washington State University’s fluorescent rock exhibit speak volumes about its dazzling impact on young visitors.
“There’s always lots of oohing and aahing when kids see them and, as you can see, they get as close as they possibly can,” said WSU geologist Kurt Wilkie. He’s one of several scientists who give tours of the S. Elroy McCaw Fluorescent Mineral Display located on campus – and who sometimes must clean the glass.
Behind the glass pane, 150 rocks glow in brilliant yellows, purples, oranges and greens. Set against a dark background, they make up a nocturnal garden that captivates adult visitors as well, said Wilkie: “They’re always asking, ‘what makes them glow?’”
Shedding light on the light
The rocks, collected from places around the globe, look like any other rock when illuminated under normal conditions. But when exposed to ultraviolet (UV) light, a reaction takes place that makes the rocks glow.
“Most rocks don’t fluoresce. It depends on the minerals that they’re laced with and whether certain impurities are present in those minerals,” said Wilkie.
Inside the geology museum of WSU’s School of the Environment, viewers enter the darkened display room by pulling aside a thick curtain. By pushing a button on the wall, they activate a UV light that makes the rocks gleam like it’s party time.
Reminiscent of the luminous black-light posters of the ‘60s, but with patterns and compositions crafted by nature millions of years ago, one artifact is metallic orange while another is grape-Popsicle purple. Some display intricate veins of colored wattage while others are drenched in it.
The rocks glide past the viewing window on a slow-rotating carousel. An amber one passes by, so radiant that it brings to mind the turn-light signal of a car.
Most objects around us are seen in reflected light. The skin of an apple, for example, reflects red light. But instead of reflecting light, these rocks can actually produce it because of their mineral composition.
“They absorb a small amount of the UV light, transform it into energy and then release it in a different wavelength that’s visible to the human eye,” said Wilkie who teaches this marvel to college students in his Geology 101 classes.
Trip the light fluorescent
In 1852, British physicist George Gabriel Stokes scientifically identified the phenomenon and coined the term “fluorescence” after the mineral fluorite, which glowed blue.
Less than a century later, a 1910 WSU alumnus named S. Elroy McCaw was collecting fluorescent rocks from places as near as Mount Spokane and New Jersey and as far as Switzerland and Romania. A civil engineer who lived near Walla Walla, Wash., McCaw “displayed his fluorescent rocks at Calgary and Mission City, Canada,” according to a post in the fall 1966 issue of WSU’s alumni magazine.
He donated the display to WSU’s department of geology in 1969 before his death. Many of the artifacts “are from mines and districts which are no longer accessible to collectors,” according to the display’s website (http://environment.wsu.edu/museum/mccaw.html).
Forty-five years after McCaw’s donation, the glowing artifacts remain accessible to students and the public. No laser beams or computer-generated special effects are necessary to reveal their wonders – just a darkened room and the push of a button.
The display is located in room 124 of WSU’s Kate B. Webster Physical Science Building. Free guided tours are available by contacting the School of the Environment at 509-335-3009 or firstname.lastname@example.org.
Linda Weiford, WSU News, 509-335-7209, email@example.com