Does anyone have an idea of the origins of this object?

[pmer27]

While cleaning out the attic I came across a box with things collected from childhood and discovered this intriguing object. It is non-magnetic, approximately 37g and appears to be of a hard dark stone material. The shape and easy fit for my "right" thumb (per photo) caught my eye again as it apparently had as a youngster. I emphasized "right" thumb because when passed to the left hand it is not as comfortable of a fit which I am assuming may indicate that it is a primitive tool. I have no recollection of where I found it, but can guess that it was most likely in the Adirondacks of New York state or in central coastal New Jersey. Thanks for all of your anticipated responses.

[studiot]

A piece of NY basalt from here ?

 

https://en.wikipedia.org/wiki/The_Palisades_(Hudson_River)

 

Are there any quarries with crushers in the area?

[Ophiolite]

I agree that basalt it the best bet. I suspect the shape and comfortable conformity to thumb are chance rather than design.

[Phi for All]

I emphasized "right" thumb because when passed to the left hand it is not as comfortable of a fit which I am assuming may indicate that it is a primitive tool.

 

"Assuming may indicate" is a tricky mind game. That something fits better in one hand than the other is supportive evidence that the item may be a tool, but alone it's not nearly enough. "Assuming" means you've jumped to the conclusion that it's a tool, while tricking yourself that handedness is an indication rather than one bit of evidence.

 

Do the edges seem capable of work? Do they seem worn, from repetitive use? Is there other evidence that supports your tool hypothesis? Can you predict what work it might have been capable of assisting with, and test your predictions against reality?

[michel123456]

It looks as a regular pentagon.

Is it comfortable at hand when you rotate it in the 5 positions?

If yes then it may likely to be a tool.

------------------

As what its origin there is no mystery: it comes from a box in your attic.

Before that it was a finding from a boy most likely in the Adirondacks of New York state or in central coastal New Jersey.

[Ophiolite]

Cooling basalt will develop microfractures arranged with a pentagonal geometry. The basalt would then fragement preferentially, during weathering, along those lines. i.e the regular pentagonal shape does not make it "likely" it is a tool.

 

One might also hypthesise that by chance perhaps one in one hundred fragments are this shape. What shape gets collected by the passer by? It isn't the random shape, but the one with a regular pattern. Selection biases the content of any collection.

[Endy0816]

Not seeing anything in images of Native American tools that looks similar. Size, shape and lack of an edge seem to be the main features that are off.

 

Unrelated, but I did come across something else I'd been looking for a reference to:

 

https://en.wikipedia.org/wiki/Roman_dodecahedron

Edited February 23, 2016 by Endy0816

[pavelcherepan]

 

 

Cooling basalt will develop microfractures arranged with a pentagonal geometry. The basalt would then fragement preferentially, during weathering, along those lines. i.e the regular pentagonal shape does not make it "likely" it is a tool.

 

Ophiolite, I've seen many times hexagonal cracking in basalts, but pentagonal symmetry doesn't appear in normal crystal structures (only really known in quasi-crystals) and hence there wouldn't be an underlying structural cause for such a fracturing. Also you can't tile a surface with pentagons in which case it should've been either a mix of hexa- and pentagonal blocks or this shape is simply due to weathering or some other later cause.

 

Edited March 18, 2016 by pavelcherepan

[StringJunky]

 

Ophiolite, I've seen many times hexagonal cracking in basalts, but pentagonal symmetry doesn't appear in normal crystal structures (only really known in quasi-crystals) and hence there wouldn't be an underlying structural cause for such a fracturing. Also you can't tile a surface with pentagons in which case it should've been either a mix of hexa- and pentagonal blocks or this shape is simply due to weathering or some other later cause.

It's called columnar jointing. You can see pentagons in this basalt pile. If you look bottom left of the structure, you can see puddles on the top of four or five columns... there's the source of the dimple in the OPs sample which is simple water erosion. You can see some drier ones adjacent to them that are clearly dished in the middle..

 

Edited March 18, 2016 by StringJunky

[pavelcherepan]

It's called columnar jointing. You can see pentagons in this basalt pile. If you look bottom left of the structure, you can see puddles on the top of four or five columns... there's the source of the dimple in the OPs sample which is simple water erosion. You can see some drier ones adjacent to them that are clearly dished in the middle..

 

 

Well, not really. Even if for some strange reason initial water pond on top of basalt column is pentagonal, as weathering continues it will circularise as in the link below:

 

https://theunwittingtraveller.files.wordpress.com/2011/07/img_2106.jpg

 

Pentagonal shape is not very common at all in rocks and minerals and even though you can have crystals growing in a shape of pentagonal dodecahedron, it's quite rare and pentagons are can not be regular as in this pyrite crystal, for example:

 

http://www.matematicasvisuales.com/images/geometry/space/dodecahedron/minerals/DSC_6424_1.JPG

 

 

 

there's the source of the dimple in the OPs sample which is simple water erosion.

 

I have some doubts about it. Water erosion removes small bits and pieces of material at a time, not chunks of >5 cm across. To have such a piece separate via weathering there should be pre-existing cracking and yet again, while not impossible but it's unlikely to have pentagonal cracks in basalt which is much more likely to have cracks in hexagonal symmetry.