🔎 UNIDENTIFIED Obsidian Look-Alike?

[Blackfoot58]

Creek walking today in SE Iowa.
Found this black, glassy rock. I’m told there was no volcanic activity in this area, so no obsidian.
I’ve found a lot of black, shiny rocks over the years, but none like this one.
It doesn’t resemble any of the various coal samples I’ve found either. Ideas welcomed. 👍🏼

 

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[blauer]

Glass.

 

[fuss]

Ya probably Slag glass.

 

[unclemac]

or perhaps dacite, I find points made of it.

 

[Clay Diggins]

It's glass. No workable Dacite in Iowa.

 

[unclemac]

it could well be glass, however don't discount trade of materials. I have obsidian points that source from over 600 miles away from where they were found.

 

[Bucket Lister]

I agree it looks like glass slag; are there any (historical) glass producers in the region?

FWIW, there is such a thing as 'blue obsidian,' and while there are no active volcanoes in IA, the same can't be said for extinct volcanoes.

Some minerals can be harder to identify without holding them and running some tests.

 

[Blackfoot58]

I agree it looks like glass slag; are there any (historical) glass producers in the region?

FWIW, there is such a thing as 'blue obsidian,' and while there are no active volcanoes in IA, the same can't be said for extinct volcanoes.

Some minerals can be harder to identify without holding them and running some tests.

It doesn’t appear to be glass slag. I’d bet on some shiny, black rock first.

 

[smokeythecat]

It's probably glass slag BUT, with that said here in Maryland on extremely great occasion we find a piece of obsidian from out west in situ on an American Indian site.

 

[Bucket Lister]

It doesn’t appear to be glass slag. I’d bet on some shiny, black rock first.

So far, you appear to be outvoted. 😉

This fracture feature on the backside suggests glass, but I'll keep an open mind.

Have you tried googling minerals or gemstones of Iowa, or the Iowa Geological Survey? I skimmed a few sites, but didn't see anything similar. If it were anything of consequence, I would think those (kinds of) sites would have something.

 

[unclemac]

...do you guys back east run into glacial till at all? Where I am I can't dig a hole 2 inches down without hitting cobbles of all kinds of stone. It is a real chore to dig a post hole.

Glacial Till and Glacial Flour (U.S. National Park Service)

Till is the sediment deposited by a glacier.

www.nps.gov

 

[Robot]

Hi Blackfoot58,​

What this rock may be is:

Hematite​

Known to be located in Iowa!
This iron ore has the same characteristics as sapphire and ruby.

It’s sturdier than pure iron and aside from black, it may also come in the color of silver or grey.

However, these rocks always have that red streak on them. When made into powder, the color of the powder is red, which is why it’s also called “haimatitē”, meaning blood-like.

Like other crystals, it’s also believed to have healing powers. Those who practice alternative healing use this rock for healing broken bones, insomnia and stress.

To determine its authenticity is by conducting a streak test. Scrape a piece of hematite across unglazed porcelain and it should produce a reddish-brown streak, a characteristic shared by all specimens of hematite.

 

[Clay Diggins]

There is no native obsidian in Iowa of any color. No matter how deep you dig.

It doesn't look like slag glass from the pics. I'm thinking it might be a piece of broken black glass from a vase or large footed bowl. The possibilities of it being broken water tumbled glass debris in Iowa is infinitely greater than it being imported unworked obsidian.

 

[smokeythecat]

Unclemac, no. The glaciers ended about 150 miles north of here. That said, there are some very odd mineral deposits in the creeks here. The basic minerals are schist, with inclusions like mica, garnet, silver, gold, titanium. But there is a 3" layer of white dolomite/marble, all finely crushed about 3' down.

 

[CreekSide]

Get some vinegar and pour it in a plastic tub. Drop it in and let it sit for about 3 days. Then let’s see it. Might be just stained from the creek. If it isn’t glass it might actually be your 1st stone artifact (broken) so clean it and let’s see

 

[Blackfoot58]

Get some vinegar and pour it in a plastic tub. Drop it in and let it sit for about 3 days. Then let’s see it. Might be just stained from the creek. If it isn’t glass it might actually be your 1st stone artifact (broken) so clean it and let’s see

I’ll give that a try. Thanks

 

[unclemac]

Unclemac, no. The glaciers ended about 150 miles north of here. That said, there are some very odd mineral deposits in the creeks here. The basic minerals are schist, with inclusions like mica, garnet, silver, gold, titanium. But there is a 3" layer of white dolomite/marble, all finely crushed about 3' down.

boy howdy let me tell you.... it must be nice to sift through nice deep black earth!

 

[Blackfoot58]

Get some vinegar and pour it in a plastic tub. Drop it in and let it sit for about 3 days. Then let’s see it. Might be just stained from the creek. If it isn’t glass it might actually be your 1st stone artifact (broken) so clean it and let’s see

Nearly 3 days submerged in white vinegar. No real change. There is a brown spot on one side (above arrow).

It’s so reflective, it looks blue, instead of jet black (like Superman’s hair in the comics). Also, it lightly scratches unglazed porcelain but leaves no color.

 

[CreekSide]

View attachment 2139064Nearly 3 days submerged in white vinegar. No real change. There is a brown spot on one side (above arrow).
View attachment 2139065
It’s so reflective, it looks blue, instead of jet black (like Superman’s hair in the comics). Also, it lightly scratches unglazed porcelain but leaves no color.

Hold it up to a light source

 

[Blackfoot58]

Hold it up to a light source

100% opaque. No light gets through it anywhere.