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Larsonite - The prettiest thing to come out of a 14 million year old bog?

Fossils and Minerals

Today, we’re talking about a distinct type of petrified bog wood that goes by many names. It is only found near McDermitt Nevada and was first mined by Gary McIntosh and Ray Larson - so you can call it McDermitt Jasper, or Gary Green Jasper, or Larsonite.  I usually call it  Larsonite because it sounds the most sciencey, and that’s just the kind of nerd I am.

Sorry Gary.


A painterly close up of Larsonite from fossilera.com. Those colors! That pattern!

This polyonymous (new word I just learned!) stone is known and loved for its attractive shades of blue and green, and well preserved wood grain patterns. Besides the rich hues, what I find most captivating about Larsonite is that it is only found in one place and tells us a story about a specific ecosystem in a specific period of time!

It all starts with the Yellowstone Hot Spot*. Today you can find it underneath Yellowstone National Park of course, but it hasn’t always been there. Over time, the North American tectonic plate has been slowly moving over the hot spot, leaving a 500 mile long trail of giant calderas. If we go back in time, somewhere around 14 million years ago, the area around northern Nevada and southeastern Oregon would be right over the hot spot.



A map of the Yellowstone Hot Spot's historic locations from nps.gov.

It’s during this part of the Miocene Epoch that the trees we see preserved today as Larsonite were once living in a boggy habitat. That is, until a series of volcanic events began producing powerful eruptions with huge amounts of ash and ejecta, knocking over trees, covering the local flora, and just generally messing things up. Unfortunate for the trees, but fortunate for geologists.

And rock lovers.

And curious ladies like me.

Uncut chunks of Larsonite from Arizona Lapidary and Gem Rough

Two things were working in our favor in this scenario. First, the trees and other material were in a bog so when they fell over they landed in a nice anaerobic (oxygen free) environment. And second, if they weren't totally submerged in the water, they were covered quickly with ash so they didn’t decay or get munched on. Perfect recipe for some first rate petrification!! Then, thanks to all the hydrothermal activity caused by the hot spot, water that was loaded up with minerals began seeping into our trees and gradually (really, really gradually) replacing the organic material with lovely things like iron, aluminum, sodium, potassium and calcium. It’s this specific cocktail of minerals that gives Larsonite it’s recognizable tones of cool teal blue to bright lime green. Neat, right?! 

 

A polished slice of Larsonite from my collection with rich greens and dash of blue!

Of course, all petrified wood is fascinating and teaches us about our planet’s history, but I am particularly awestruck by how Larsonite helps scientists pinpoint specific events and create such a complete picture of a past environment while being super gorgeous at the same time. Working with and wearing these ancient treasures feels like such an honor, I hope you appreciate their story and their beauty as well! You can click here to see what Larsonite creations I have available right now, or feel to reach out to see if I have anything new in the works!

 

Larsonite is mined near McDermitt, Nevada - the ancestral land of the Northern Paiute. The Fort McDermitt Paiute and Shoshone Tribes of the Fort McDermitt Reservation live in the region today.

* a volcanic hot spot is basically a place where there has been a lot of volcanic activity over a long period of time. It’s thought that these spots are places where the mantle is hotter than normal and is able to push up through the crust. The Hawaiian Islands give us a good look at how hot spots work. The chain of islands were formed as the tectonic plate slowly moved over the area of volcanic activity, creating a series of land masses as the lava and ash spewed out. 

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