Glass Buttes obsidian field trip

Glass Buttes Flint knappers camp 1May2018

Glass Buttes Flint knapper’s camp

I went on a field trip recently to one of my favorite places–Glass Buttes. Obsidian is everywhere you look! It’s like being a kid in a candy store. In fact in one of my previous posts, Glass Butte Dragonglass, I show a picture of some obsidian I have collected displayed in a candy bowl.

Obsidian at Glass Buttes, OR 1May2018

Obsidian everywhere you look!

Glass Buttes – Rockhounding and habitat

Located about halfway between the towns of Bend and Burns in eastern Oregon, this site is a rockhounder’s paradise. You can dig and crack open obsidian with a rock hammer, but you really don’t need to because it’s all over the surface.  The Bureau of Land Management oversees most of this site. Individuals may collect up to 250 pounds of obsidian per year.

Glass Buttes, Oregon 1May2018

Glass Buttes, Oregon

Glass Butte, elevation 6,388 ft., and Little Glass Butte, elevation 6,155 ft., tower over the surrounding hills. Sagebrush, rabbitbrush, and bunchgrass cover the landscape. Western juniper and mountain mahogany are interspersed over the land. Sagebrush-dependent species such as Brewer’s sparrows, sagebrush sparrows, and sage thrashers were seen and heard the day we were there. A pair of mountain bluebirds was seen perching high in the juniper trees. We caught glimpses of ferruginous hawks.

Mountain bluebird pair at Glass Buttes, OR 1May2018

Mountain bluebird pair

Geological history of Glass Buttes

Glass Buttes formed during the Miocene and Pliocene periods, 5-5.8 million years ago. Three layers of lava flows from volcanic domes and vents formed the buttes. The first flow was basalt, the second rhyolitic lava, and the third another layer of basalt. Rhyolite contains a high percentage of silica and it forms much of the substrate. Due to a rapid rate of cooling of magma at Glass Buttes, larger mineral crystals didn’t have time to form. The silica-rich “glass” of obsidian formed as a result of this process.

Lichen Painted Rhyolite Rock 1May2018

Lichen covered Rhyolite rock

Here’s an interesting article with more details about the obsidian at Glass Buttes for you geology geeks. Obsidian is Hot Stuff.

This area is in the Brothers Fault Zone of the High Lava Plains physiographic province. The many faults are easily observed in aerial photos and through the use of Light Detection and Ranging (LiDAR) data. A 2011 map of Glass Buttes based on LiDAR can be seen here.

Desert Driftwood

Desert Driftwood

Flint knappers then and now

Obsidian from Glass Buttes has been used in making tools for thousands of years. Native Americans made arrowheads, spear points, and other cutting tools with the glass-like stone. Obsidian from this site has been found throughout western North America.

Lupine at Glass Buttes 1May2018

Lupine at Glass Buttes

Modern day flint knappers take advantage of the abundance of obsidian at this site. Some groups meet annually at events such as the Glass Buttes Knap-in to work on their craft. My first photo on this post shows what flint knappers left behind at one of their campsites.

Types of obsidian at Glass Buttes

There are MANY types of obsidian at Glass Buttes. I will quote Tim Fisher who runs the Oregon Rockhounds Online website. “Need a list of what’s here? OK, here goes: black/mahogany, leopardskin, mahogany, Midnite lace, triple flow, double flow, pumpkin, purple and silver sheen, gold sheen, silver sheen, rainbow, peacock, purple sheen, fire, green, Aurora Borealis rainbow, black, opaque black, opaque banded, gunmetal, and probably many more!” If you want detailed information on where to find the different types, please purchase the Ore Rock On guide from his website. We own it and it contains invaluable info for sites in Oregon, Washington, Idaho and western Montana.

Glass Buttes Aurora Borealis Obsidian Photo by Tim Fisher

Glass Buttes Aurora Borealis Obsidian – Photo by Tim Fisher

Some rockhounds search for specific types, such as rainbow and fire obsidian, and they can be the most difficult to find.

Other land use

We made a couple additional short stops on the field trip. We stopped at an abandoned mercury-bearing cinnabar mine. The site was discovered in 1933 and mined until 1957. Another stop was made at an exploratory geothermal well site. No development is currently taking place but it may happen in the future. Greater sage-grouse live and breed here and that may limit development.

Obsidian-paved road at Glass Buttes 1May2018

Obsidian-paved road at Glass Buttes

Additional information

This is a great area to visit but I should remind you of a couple things. Obsidian is SHARP so make sure you have good tires and a spare tire. Four-wheel drive vehicles are recommended for certain areas. There is no water or facilities here. If you visit, be prepared. Access to this site is on an unmarked road near mile marker 77 on Highway 20. Drive south a couple miles to find obsidian. Additional information is available from the organizations listed here.

I have been to this site several times. My recent trip was with Bend Parks and Recreation. I always wish I could stay at Glass Buttes just a little bit longer. It’s a hard place to leave if you love rocks!

 

6 thoughts on “Glass Buttes obsidian field trip

  1. Very interesting stuff! 🙂
    Yes, many people do not realize that the Native American tribes traded with each other over great distances. Many were specialty-makers, such as in the making of certain designs of arrowheads or decorative wear. They were quite sophisticated as a society. Of course, they didn’t teach us any of this when we were in school.

    • Thanks! I thought you might like this post.

      I am sad that much of our history was glossed over or not covered at all. There is so much to learn…

  2. When I was younger, I was a big rock collector. Once, I was about 7, I ran away from home, I made it maybe a quarter mile from home, and I found a rock that I HAD to put in my rock collection. So I didn’t run away and went back home.
    One of my favorite pieces was a piece of polished obsidian, black, about the size of a marble. When you held it up o the light, you could see through it! My little sister still has my rock collection, including that obsidian.

    • You sound like a rock collector from way back. I have several pieces of transparent obsidian. It is an amazing stone!

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