Rock/fossil Id

[MuseumGirl]

Found these in a museum closet - any help with IDing them? Sorry for the poor photo quality.

- dark one with white tubes that go all the way through - calcite coral or worm tubes?

- grey one with black inclusion - slag?

Thanks!

[Fossildude19]

First looks like a coral - something akin to Syringopora sp.

The second one, I'm afraid the pic is too blurry to make out any detail.

Does the black inclusion have uniform,tiny dents in it?

Regards,

[MuseumGirl]

Thank you!

For the second one - there doesn't appear to be any structure in the black sphere. Depending on how small you mean by "small dents" there are a few tiny what I would call scratches on it but that's really about it. Here are a few more pictures but again, not the best quality without access to my camera today.

[Fossildude19]

I'm thinking a mineral inclusion of some sort, but that is beyond my area of knowledge. Maybe one of the mineral guys will weigh in.

Regards,

[BobWill]

Welcome to the forum. How odd for a museum to store something without documentation, but good for you taking the initiative to find out something. I agree with Tim about the coral and I had a sample of the other specimen given to me by someone from Memphis but I gave it away along with the description

I think it's a kind of quartz with a mineral deposit maybe something like obsidian. it has a Native American common name but someone on here will probably know. You can see where more of the deposits were in the cavities and fell out.

Edited September 18, 2014 by BobWill

[MuseumGirl]

We are a museum that has an exhibit where kids can "trade" items that they find which means we often find items in the storage closet that were unidentifiable by the volunteer running the exhibit at the time and they often come without information or the kids says "my grandpa gave it to me," etc. Then we have to play the wild goose chase game to identify with no information.

- the structure is not consistent throughout: some areas are laminated like mica, others are small crystals that appear quartz-like. Some areas have cleavage planes, some appear to have conchoidal fracturing.

Edited September 18, 2014 by MuseumGirl

[painshill]

I'm not convinced the first item is a fossil, as opposed to something igneous and amygdaloidal (basalt? andesite?) but the picture isn't too sharp.

Bob's right about the second one I think. It looks like an obsidian nodule of the kind colloquially known as "Apache tears". The matrix is likely largely composed of perlite or well on it's way to becoming so (it's the hydrated weathering product of obsidian). Like this one:

Incidentally, there's no way the nodule came from Ohio originally (or the other specimen if it's igneous). No igneous exposures in Ohio... only sedimentary plus glacial erratics that don't include obsidian. Obsidian is generally only found west of the Mississippi.

[MuseumGirl]

Thanks so much! Yes, of course not from Ohio...we get objects from around the world which again leads to a lot of time searching for information on items as they are not something we see often.

[John K]

I'm not convinced the first item is a fossil, as opposed to something igneous and amygdaloidal (basalt? andesite?) but the picture isn't too sharp.

Bob's right about the second one I think. It looks like an obsidian nodule of the kind colloquially known as "Apache tears". The matrix is likely largely composed of perlite or well on it's way to becoming so (it's the hydrated weathering product of obsidian). Like this one:

Obsidian Nodule.jpg

Incidentally, there's no way the nodule came from Ohio originally (or the other specimen if it's igneous). No igneous exposures in Ohio... only sedimentary plus glacial erratics that don't include obsidian. Obsidian is generally only found west of the Mississippi.

I was searching the dark, dusty parts of my brain for where I'd seen the black inclusion image before - painshill hit it right on the nose. And I agree with the ID of the first - my first thought was that it was a cobble of basalt with some sort of mineral inclusions (quartz, prehnite, olivine, etc.)

Edited September 18, 2014 by John K

[MuseumGirl]

These are a little better:

Appear to be tubes that run all the way through the matrix.

Edited September 18, 2014 by MuseumGirl

[painshill]

Thanks John

There's an interesting Native American back-story associated with Apache tears:

http://en.wikipedia.org/wiki/Apache_tears

Thanks for the better pictures MuseumGirl. They popped up as I was typing, so I'm just about to have a better look.

[painshill]

Well, I don't know what it is but I don't think it's mineralogical based on those pictures. When amygdules are elongated (pipe amygdules) the alignment is almost always perpendicular to the flow for all of them... not a mixture of arrangements. I also see a small spiral which is not impossible in magmatic rocks... they're known as "curlicues" and are caused by frictional drag between the bedrock and the flow of the magma. But they're usually rather bigger and occur in the matrix, not the amygdules. I'm leaning towards coral.

[MuseumGirl]

Thank you guys for all your help! I've got the local stuff down pat along with the common stuff from getting my geology degree but I'm sure I will be posting other odds and ends again soon.

[TqB]

Definitely a coral, complete with typical budding patterns. (Check out Siphonodendron and Diphyphyllum from the Carboniferous, as well as Syringopora, for something at least similar).

Polishing or wetting the surface should help to narrow it down.

[Herb]

the matrix does not appear to be anything I am familiar with in Ohio. My guess is they are glacial in origin. Very interesting specimens.

[Plax]

second one looks like very hard cast and mold limestone or dolomite with perhaps a worn paleozoic fish tooth or other phosphatic remnant, but it's just an overall look I can't make out details

[howard_l]

Even though Ohio has no Igneous bedrock exposures because of all the glacial material there are creek areas that have very abundant Igneous and Metamorphic material.

[painshill]

Even though Ohio has no Igneous bedrock exposures because of all the glacial material there are creek areas that have very abundant Igneous and Metamorphic material.

Yes, I recognised that in my post... but not obsidian. There is in any case no need to suppose a glacial origin since it's not being said that either specimen actually originated in Ohio. The obsidian nodule likely came from Arizona in someone's pocket.