Obsidian and a tooth (?) in concrete

[Lisa Millbank]

We got some chunks of broken concrete from our neighbors after they tore up their old patio with a jackhammer.  We're reusing them for a yard project, but Don noticed that there's a split piece of obsidian in one of the chunks.  Then I found a small tooth-like thing that was part of the pea gravel base on which the concrete was poured.

The obsidian piece is a round river rock about an inch across.  It's not too hard to find obsidian flakes at a few sites around Corvallis (waste from pressure flaking to make tools/weapons), but we've never found a piece like this.  I thought that people from the mid- or southern Willamette Valley, like the Kalapuya, had to make an arduous trek into the Cascades or trade with somebody else to get obsidian.  I learned from this archaeology paper about human use of obsidian in the Willamette Valley that there's a deposit of obsidian river rocks close to Eugene, at Inman Creek.  That obsidian must have eroded out of a source in the western Cascades that hasn't been located, and was deposited at an old meander of the Willamette River.  Scientists use chemical and physical characteristics of obsidian to identify the source it came from, and the paper says that 80-100% of obsidian artifacts from the Corvallis area come from Inman Creek obsidian.  Local people may have gotten some from the source location and some from pieces that washed downstream and were found locally along the river.  This particular piece in the concrete was probably just another one that washed downstream from that deposit and ended up among some river gravel that was mined for use as aggregate.

The tooth (if that's what it actually is) is broken and spent a long time being tumbled in river gravel, so the original shape has been rounded off a lot.  We tried to scratch glass with it, but it's too soft to scratch it, as a tooth would be.  It's about 15mm long and has a distinctive curved groove that runs longitudinally toward the point, similar to the groove on carnivore canines, although I have no idea what critter it's from.  One side has a more polished surface and the other side is broken.  The smoother surface has tiny striations, and the broken surface shows a complex structure.  At the wide end, the material is rougher, more porous and a different shade.  If anyone has input, let me know--maybe it's not even a tooth at all.

Lisa Millbank

[Randy and Pamela Comeleo]

https://youtu.be/ulAn1YCalSU

Randy (and Pam)

[Don Boucher]

Thanks Randy,

That's funny! It's a good reflex for the little frogs to hop away. On time at E.E. Wilson years ago, I saw a yellowlegs gulp down a young bull frog. It was nearly too big to fit down the yelloweg's gullet.

-Don Boucher

On Sat, Oct 9, 2021 at 2:15 PM Randy and Pamela Comeleo <rott...@peak.org> wrote:

https://youtu.be/ulAn1YCalSU

Randy (and Pam)

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[Mary Garrard]

Funny! Except not for the frogs. The yellowlegs didn’t seem to be that interested in them. 

Mary

[Randy and Pamela Comeleo]

Just before I shot the video we watched in disbelief as a yellowlegs grabbed one of the larger bullfrogs, tossed it around a bit, and then gulped it down when approached by a couple of other yellowlegs!

Randy (and Pam)

---

From: "Mary Garrard" <spring...@gmail.com>
To: "rottyler" <rott...@peak.org>
Cc: "mid-valley-nature" <mid-vall...@googlegroups.com>
Sent: Saturday, October 9, 2021 3:02:52 PM
Subject: Re: [MidValleyNature:6197] Eek!  It's the Yellowlegs!

[Adrienne]

Thank you for this video. Are these little baby bullfrogs? They are invasive. I'm happy to hear the yellowlegs are able to eat the bullfrogs.

Adrienne

[Amy Hill]

Could the "tooth" be a tiny piece of petrified wood, perhaps?

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[Tanya Lasswell]

[Google Groups told me I need an editor by not allowing me to send my previous post, so here is a shorter version]:

This past summer we found some lovely rocks (that are very similar to yours, Lisa) on the bank of the Mary's River. We also found some gorgeous crystals in some gravel we purchased from a nearby quarry, and due to an accident with a 4-year-old, a dishwasher, and these crystals, we were able to link the two! The first image attached is some rocks before cleaning (BC), and the second is after dishwasher (AD).

I now had another excuse to do a little internet 'digging' for rock origins (because it's a global pandemic and I have 2 small kids at home, and few other creative outlets).

This is what we came up with for our specimens: Oregon Coast zeolite. They are filamentous sodium calcium alumino-silicate crystals (which I just-so-happened to know LOTS about because we had just removed 65 garbage bags of asbestos-containing vermiculite removed from our new house, and I thought it prudent to know about zeolites). I can't pin down a more precise name, unfortunately, as these look like mesolite, thomsonite, and natrolite. (Despite being well-versed in biological taxonomy, the taxonomy of rocks completely eludes me.) 

Regardless, as near as I can tell, they are formed by lower-temperature crystallization between bubbles made when underwater volcanoes burp up lava. Here is a lovely picture of some zeolites in their native basalt up on Mary's Peak, which is exactly like what my gravel looks like (except in larger pieces). The pillow basalt they are cradled between is beautiful as well! The pillow basalt is from the Eocene Siletz River Volcanics, which is an interesting bit all it's own. However, one avenue of current thinking attributes these lava bubbles to a mantle plume, possibly the Yellowstone Hotspot! I'm rather excited that we managed to move to one of the few places where the Siletz terrane pokes up out of the ground for viewing, and that it's origin is still under active research. :)

It's a little surprising there isn't more about our pretty zeolites on the internet - they are so interesting looking. And no one we've asked (ok, we are still new here and know probably 4 people) seems to have noticed them?!? We may have to join the online show-and-tell 'Geology Rocks' meeting of GSOC (Geological Society of the Oregon Country) this weekend. Or one of these days.

Lisa, I'm not sure this is what you have, but I thought I'd share.

All the best,

Tanya

[Joel Geier]

Great suggestion! I didn't think of that, even though I pretend to be a geologist (really a hydrogeologist who has never been very good at hand-specimen lithology).

Hurray for your 4-year-old's inspiration to conduct a scientific experiment on turbulent abrasion of those crystals. Too many of us adults have lost the creative instincts to conduct that kind of fundamental experiment. And that must be a powerful dishwasher!

Joel

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From: "Tanya Lasswell" <tanya.l...@gmail.com>
To: "Mid-Valley Nature" <mid-vall...@googlegroups.com>
Sent: Sunday, October 10, 2021 5:55:41 PM
Subject: [MidValleyNature:6212] Re: Obsidian and a tooth (?) in concrete

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[Lisa Millbank]

Hi Tanya and all,

That's a good suggestion for the "tooth" that we didn't think of.  I'm pretty sure that the crystals we see in crushed rock around here are mesolite, and it definitely has a unique, striated appearance.  On Mary's Peak, similar crystals are supposedly natrolite; I don't know if I could tell the difference.  It actually wouldn't be too unlikely to find this mineral in river gravel.  On Mt. Pisgah near Eugene, there are supposedly "chatoyant" mesolite crystals, I guess they show a similar optical phenomenon to polished cat's eye. 

I still don't know what this object is because it's not easy to scratch with a knife or a steel file, but it's not as hard as glass.  The samples you found eroded so severely on their trip through the dishwasher that they seem quite a bit softer than what I have.  However, the post-dishwasher version does look fairly similar to the mystery object.

I tried Joel's suggestion of exposing it to acid, thinking that the calcium in a tooth would bubble.  I tried concentrated citric, glycolic and sulfamic acid, but none of it caused obvious bubbling.  Maybe the acids weren't strong enough, or I didn't leave it in the acid long enough to really tell.  I don't know that I'm going to put more time into trying to figure it out, but I appreciate all the suggestions and insights into what it might be.

Lisa

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