Helenite: can volcanoes really weep gems?

If you are on this blog, you know I’m a nerd. You’re probably a nerd too. Have you ever considered your nerd origin story? Mine began at age 7 or so in the basement of my grandparents’ house in Ottawa, Canada. Behind the washing machine and toy trains, the walls were lined with DECADES of National Geographic Magazines to pore over while the grown-ups wanted me out of their hair. When I was 9 they gave me a subscription so I could amass my very own giant yellow pile of nerdy heaven with priceless pull-out maps. I have an everlasting affection for this magazine. But it’s not the main content of the magazine I want to write about today.

It’s the ads.

In every edition, there’s at least one ad selling the reader some rare, shiny thing – a coin or a gem. The format hasn’t changed since at least 1975. The ad is full of small text raving about the product. There’s a close up with photoshopped sparkles, and a free gift with purchase. This month’s shiny trinket feature seemed tailor-made to my inner magpie. Gems? From a volcano? In my state? How can I be a geologist and never learn about a volcano spitting out gems before!

It, uh, turns out that volcanoes don’t actually spit out gems. More on that in a bit.

First off let me point out some of the positives from this ad, lest I seem too harsh. Helenite is shiny! very green! fairly cheap! 3/3 for Courtney’s inner magpie points. But there is a suspicious amount of purple prose in the ad. Let’s see what a quick google search will reveal.

The ad implies that helenite is a gem linked to the eruption. It weasels out of saying that the gem is naturally created or manufactured, but most people automatically link gems with being natural. The ad also hypes its rarity. Unfortunately they are false on both points.

Mount St. Helens erupted in 1980 in the southwestern corner of Washington, and blanketed the surrounding area in 540 million tons of ash. To give some context, 540 million tons is equivalent to 531.5 USS Nimitz nuclear powered aircraft carriers. Is the raw material rare? You be the judge.

USGS map of ash distribution

The suddenly ashen forest immediately surrounding the mountain was owned and logged by the Weyerhaeuser Company. The helenite legend goes that when Weyerhaeuser went in to salvage their equipment that had been caught in the crossfire, they found a strange effect. Their acetylene torches reacted strangely with the ash as they tried to free their machines. The heat from the torches fused the ash into a novel green glass.

Photo of uncut helenite, from geologyin.com

Of course anything shiny will draw people trying to make a buck, so now helenite is marketed and readily available as a cheap alternative to emerald, or as a souvenir. It’s softness gives it away – it’s only about 5.5 on the Mohr’s hardness scale that ranges from 1 (powdery) to 10 (diamond). An emerald scores 7.5 to 8 on that scale. Manufacturers also add cobalt or gold powder to add a blue or red tint to the finished product, so helenite is sold in a range of colors besides green.

And there have been some studies done that cast doubt on whether helenite is actually made of pure Mount St. Helens ash after all. A 1988 study published in Gems & Gemology melted known Mount St. Helens ash and compared it to a s purchased specimen of helenite. The study found that melted ash from the eruption looked like obsidian – dark gray, not green. The author used x-ray fluorescence and found out that the ash had much more iron and titanium in it which gave the dark gray melted ash its color, and higher quantities of aluminum which made the melted ash melt at a much higher temperature. The genuine Mount St. Helens’ ash melted at 1,300 degrees F, while the helenite melted at 800 degrees F. This variation is much more than you would expect, even given that ash composition within an eruption can vary. I made the dual pie charts from the information in the paper to compare the composition of genuine ash with the composition of green glass…

Even with some canny google searching and combing through the US Patent office, I couldn’t find out who actually manufactures helenite that is sold by jewelers, or how they obtain the ash. Maybe I just have to do an Indiana Jones style Hunt for the Helenite when this COVID-19 thing is over?

All this being said, I would absolutely buy helenite in a gift shop. Especially if it came in teal. After all, my inner 9 year old National Geographic-reading nerd is not that far from the surface.









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