What's Behind the Gemstones 'Raining' From the Kilauea Volcano


Lava spews from a new fissure on Luana Street after the eruption of Hawaii's Kilauea volcano on May 5, 2018. But likely, no olivine came from it. U.S. Geological Survey via Getty Images

In mid-May Mount Kilauea in Hawaii erupted violently, sending a plume of debris soaring 30,000 feet into the sky. Since then, the very active shield volcano has been spewing hot magma and ash, destroying around 600 homes. As an ostensible encore, this week, social media exploded with reports of gemstones "raining" from the sky nearby, sending bystanders scurrying to collect evidence of the once-in-a-lifetime event.

The gems in question are part of a rock-forming group of minerals called olivine, a type of magnesium iron silicate that's more commonly known by its gemstone name, peridot. Olivine is by no means rare on Hawaii. It's found in huge amounts in rocks all over the area and on the islands' beaches, which in some places take on a greenish hue thanks to the ubiquitous mineral.

Olivine is often found in basaltic lava, the kind that Kilauea is producing during the current eruption. It forms deep in the earth, until a brew of hot magma pushes it up to the surface. The igneous rocks that result from cooling lava frequently contain olivine, which may be released during erosion or explosive events.

Olivine washes up on Papakolea Beach in Hawaii, one of four green sand beaches in the world. The green sand is found in basaltic lava.
paranyu pithayarungsarit/Getty Images

The olivine that people are finding "raining" from the sky is likely just a byproduct of explosive events from Kilauea's current tantrums, and probably cooling lava, too. Some of it may even have been from past eruptions, and people are just now noticing it. Geologists say this current volcano doesn't have a lot of olivine.

Most of the stuff is too small for jewelry and not of gem quality. Plus, it's actually illegal for visitors to remove lava rocks, sand or olivine from the islands.

For those of you intrigued by the idea of hunting for rocks near a still-active volcano, keep in mind that doing so might pose a hazard to your health. Kilauea is still upchucking rocks and debris, along with lava, that can hurt or kill people, particularly where lava oozes into seawater.


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