Glow-in-the-Dark Mine

Only a few dim lamps light the way as a guide leads visitors down a carved passageway into a former mine in New Jersey. The group stops when it reaches a spot called the Rainbow Tunnel. The guide turns off the overhead bulbs and flips on ones with invisible ultraviolet (UV) light. The once dull rock walls suddenly glow brilliant shades of red, green, blue, and orange. It’s like looking at a rainbow underground.

The vibrant tunnel is just one of the glowing wonders you can glimpse at the Sterling Hill Mining Museum. Above ground, the museum displays the world’s largest collection of fluorescent minerals, which have the ability to absorb and emit light. Many specimens come from the mine itself, while others come from around the globe. “Out of about 4,000 minerals known to science, only 4 to 5 percent can fluoresce,” says museum director William Kroth. Half of those can be found at Sterling Hill.

A guide leads visitors down a carved tunnel. Only a few dim lamps light the way into this former mine in New Jersey. The group stops at a spot called the Rainbow Tunnel. The guide turns off the overhead bulbs and flips on ones with invisible ultraviolet (UV) light. The rock walls had looked dull. But suddenly, they glow bright shades of red, green, blue, and orange. It’s like looking at a rainbow underground.

You can see the colorful tunnel and other glowing wonders at the Sterling Hill Mining Museum. Above ground, the museum displays the world’s largest collection of fluorescent minerals. These minerals can absorb and release light. Many samples come from this mine. Others come from around the globe. “Out of about 4,000 minerals known to science, only 4 to 5 percent can fluoresce,” says museum director William Kroth. Half of those can be found at Sterling Hill.

Workers began mining the metal zinc (Zn) at Sterling Hill in 1792. But it wasn’t until the early 20th century that they discovered the mine’s glowing secret. When miners began using electric lights instead of candles, they noticed that sparks emitted by the big, old-fashioned electrical switches sometimes caused the rock walls to glow. That’s because the sparks emitted some ultraviolet light.

Fluorescent rocks, like those found at Sterling Hill, glow because they contain small amounts of certain elements, such as the metals boron (B), lead (Pb), and manganese (Mn). When light of a particular wavelength—the distance between a wave’s peaks—hits these elements, they release a wavelength of a different color (see Lighting Up).

Workers began to mine the metal zinc (Zn) at Sterling Hill in 1792. But they didn’t discover the mine’s glowing secret until the early 20th century. That’s when miners began using electric lights instead of candles. The big, old-fashioned electrical switches produced sparks. The miners noticed that the sparks made the rock walls glow. That’s because the sparks released some ultraviolet light.

Why do fluorescent rocks, like the ones at Sterling Hill, glow? They contain small amounts of certain elements, such as the metals boron (B), lead (Pb), and manganese (Mn). Light comes in different wavelengths. Wavelength means the distance between a wave’s peaks. When light of a certain wavelength hits these elements, they release a wavelength of a different color (see Lighting Up).

Sterling Hill closed its mining operations in 1986 and reopened as a museum four years later. Since then, it has welcomed hundreds of thousands of people. Visitors can examine nearly 700 glowing specimens. And best of all, they can go underground to see dazzling fluorescent rocks glowing in the darkness.

Sterling Hill closed its mine in 1986. It opened again as a museum four years later. Hundreds of thousands of people have visited since then. Visitors can look at nearly 700 glowing samples. And best of all, they can go underground to see shining fluorescent rocks glow in the darkness.