If you want to ride the waves along this rugged coastline, you’re going to need a very, very tiny surfboard. What appears to be a gull’s-eye view of the ocean crashing on a rocky shore is actually a microscopic image of a gem called a prase opal.

The green part of the specimen is the opal, while the brown “coastline” is the host rock, “a silica and iron-altered serpentinite,” says professional gemologist Nathan Renfro, who captured the image. “The turbulent-looking white areas are most likely small fluid inclusions that make the opal appear whitish due to light scatter,” he adds. “These areas resemble the whitecaps on crashing waves, which is the detail that really drives home the aerial perspective of an oceanic shoreline.”

As the manager of colored stones for the Carlsbad, California, and New York offices of the Gemological Institute of America, Renfro’s work includes providing identification and geographic origin reports for various gemstones. He’s also an avid, award-winning microscopist—his shot of the tiny prase opal shoreline earned an honorable mention in the 2019 Olympus Image of the Year awards.

Renfro says it’s the special qualities of a prase opal that made the image possible. “Opal is made of silica spheres that, when arranged in an orderly fashion, create a phenomenon known as ‘play-of-color,’ which appears as flashes of color as you move the gem,” says Renfro. “When these silica spheres are not arranged in an orderly fashion, you get common opal.” While the gemstone isn’t flashy, it does come in many different colors, based on impurities present. “When common opal is colored by trace amounts of nickel,” Renfro says, “You get this wonderful green variety, which is known as ‘prase opal.’”

Prase opal samples from Iyobo Mountain in Tanzania.
Prase opal samples from Iyobo Mountain in Tanzania. Photo by Robert Weldon/GIA

The stone Renfro photographed comes from Haneti, in central Tanzania, at a mine located at the top of Iyobo Mountain, where prase opal has been collected for more than three decades. The eye-catching prase opal closeup is just one of the wondrous and sometimes mind-bending images Renfro has created, many of which he posts on Instagram. “Instead of exploring some uncharted wilderness or jungle, I get to explore the uncharted territory that lies in each gem,” he says. “I often get surprised by the natural beauty and remarkable features that I encounter. Taking a photo of my observations allows me to document my exploration and share the adventure with others.”