Naked Science Forum

Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Chris Palmer on 18/12/2015 18:02:40

Title: What gives a rock a dark, rusty interior?
Post by: Chris Palmer on 18/12/2015 18:02:40

This was found in the southeastern part of the United States. You can see the size of the rock from the pictures, about the size of your fist. It weighs about 2 pounds and has a few interesting characteristics:

1) It fits your hand like a tool using the 'bottom side' as a tool that might smash or break something.
2) The bottom side looks as if it was purposely made for this purpose.
3) There is rust-dust on a few locations suggesting that this has an iron core. I do not have a strong magnet but the small one I do have does exhibit force when placed near the rock.

Now, I'm a biologist and from what I gathered, this is a typed of layered metamorphic rock. I am thinking that this might have been formed from a meteorite strike that somehow formed a rock layer on its surface.

I'll stop there before I make too much more of a fool of myself and see how the responses go. I have yet to take it to a local university mainly because there is not a full geology department here.

Thanks

Title: Re: Rock identification....Iron center with rock surface
Post by: RD on 18/12/2015 19:33:25

The material looks like the flint used to make tools ...

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http://www.colchestertreasurehunting.co.uk/e/earlyhistory.htm

But that doesn't necessarily mean it is a tool.

[ definitely no meteorites involved ]

Title: Re: Rock identification....Iron center with rock surface
Post by: Chris Palmer on 18/12/2015 20:00:50

Thank you for the reply. How would you account for the rust leaching from the inside to the outside of the surface?

Title: Re: Rock identification....Iron center with rock surface
Post by: RD on 18/12/2015 20:07:47

The rust could be staining if it was used for grinding ochre (https://en.wikipedia.org/wiki/Ochre#In_North_America) ,
 similar to this ...
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http://activeartist.net/native-paint-revealed/

Title: Re: Rock identification....Iron center with rock surface
Post by: Chris Palmer on 23/12/2015 00:15:40

Okay, well it's definitely not ochre and it is a metal/rust residue. I located another stronger magnet and there is defintely a magnetic force felt so there is an iron center within the rock. There are two non-flat, sharp, depressions on the rock that have the same rust leaching and these area could not be used for grinding or smoothing a surface.

Thank you for the help and I'll continue investigating where I can.

Title: Re: What gives a rock a dark, rusty interior?
Post by: RD on 23/12/2015 09:35:25

Another possible explanation for [exogenous] rusty-stain on flint ...

Quote from: stoneagetools.co.uk

(https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.stoneagetools.co.uk%2Fimages%2FDsc_2531-ed.jpg&hash=117aec43ebecc4988a8831f1e4f4e0ee)
Rust-like spots sometimes form on the ridges of patinated flints.
They are known as 'iron-mould'.

http://www.stoneagetools.co.uk/what-is-flint.htm

Title: Re: What gives a rock a dark, rusty interior?
Post by: Space Flow on 23/12/2015 09:47:21

It certainly looks like flint...