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mickiver

Could Be An Egg.......

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bdevey

Horse gallstone or kidneystone?

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Batty

Horse gallstone or kidneystone?

Ouch. But too round I think.

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Auspex

We're spinning our wheels speculating on what it looks like; it would be very useful to determine what it is made of. Streak test, hardness, specific gravity...

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painshill

We're spinning our wheels speculating on what it looks like; it would be very useful to determine what it is made of. Streak test, hardness, specific gravity...

Thanks Chas… the voice of reason as always. I think it’s completely pointless to just suggest everything one can think of that’s “round” in the hope of providing a correct identification. It’s the (as yet undisclosed) properties coupled with a bit of logic that are gonna identify it.

Some things we can rule out straight away. It’s not a Minié ball, or any other kind of muzzle-loaded rifle shot. Way too big... it’s over an inch in diameter. Even a “Brown Bess” doesn’t have shot of that calibre. It could conceivably be “grapeshot” or “canister shot” from a cannon, but that would be lead or lead alloy. The density would tell us if it’s within range.

It’s definitely not a tektite. Apart from the fact that South Dakota is a very long way from either of the two known American strewnfields, tektites (which can be spherical) are glassy in texture (with a density close to that of man-made glass) and have numerous surface vesicles. And before anyone makes the suggestion… it’s not a meteorite!

It could well be a milling ball, but those are most usually almost perfectly spherical… which that one isn’t. But it’s not magnetic and an iron or steel milling ball would be. If it were a more modern item from a high tech hard alloy (tungsten would be most likely), it would be extremely heavy; or if from a high tech ceramic, less so, but still perfectly spherical.

I don’t see anything egg-like about it and have some difficulty persuading myself that a large fossil pearl was just laying around in some sod in South Dakota without associated shelly or other marine fossil debris.

The most helpful starter would be its density. Since it’s approximately spherical, its density could be easily calculated from a more precise weight than “about the same as an AA battery”. The volume of a sphere is 4/3 x 3.14 x the cube of the radius.

A streak test would give us some information about the mineral content – if it is a mineral. I’m leaning towards it being a hematite/goethite concretion of the type known as “Moqui marbles” when found in Utah, Colorado, Arizona and Nevada. But they occur anywhere there is iron-rich sandstone. They’re not normally magnetic (some exceptions) and most usually have a pitted surface (some exceptions again) but they are frequently spherical and may have a dimple or what looks like a “bite” taken out of them. Like these:

post-6208-0-41198900-1374172792_thumb.jpg

I also don’t see any reason why it has to be anything other than a spherical nodule out of say flint or chert. It’s not unusual to find spherical ones, like this:

post-6208-0-87346400-1374172810_thumb.jpg

Over here in the UK they’re colloquially known as “Viking balls” although they have nothing whatsoever to do with Vikings but there is some evidence of them being collected (possibly for use as slingshot stones) in ancient times.

Edited by painshill

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jpc

Edit: just tried the pearl/ vinegar experiment and got bubbles, it would take a while but it would work.

Please don't try with fossilized pearls or your wives.

I don't often play Grammar Police here but this made me laugh out loud. I will certainly not try to dunk any of my wives in vinegar. Neither will I do it with my wife's pearls.

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mickiver

I will make every effort to work out the specific gravity next week. By chance does anyone know the specific gravity of a fossil pearl? Or their wife?

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Auspex

...By chance does anyone know the specific gravity of a fossil pearl? Or their wife?

Variable, but one carries substantially more gravitas that the other...

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Indy

Variable, but one carries substantially more gravitas that the other...

Voice of experience ??

:P

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Auspex

Voice of experience ??

:P

Let's just say that I am at least aware of how little I know about fossil pearls...

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Batty

Doh!!

She a bit vinegary that one.

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ckmerlin

Moqui marbles--type of concretion hmm not sure , graphite spheres these can occur naturally but are usually quite small

sorry not much help :(

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Indy

Wondering who mickiver could take this specimen to locally

who would be able to ID it ??

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jgcox

Just a wild guess but could these be a product of volcanic activity? Where the lava fell into water and small amounts formed irregular spheres?

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mickiver

Weight = 32.6 grams

I'll determine the specific gravity later this week once my graduated cylinder arrives.

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painshill

Weight = 32.6 grams

I'll determine the specific gravity later this week once my graduated cylinder arrives.

Your initial pics show it to have an approximate diameter of 3.2cm so (treating it as a perfect sphere) the density is gonna be in the region of 1.9g/cc. That's too low for a milling ball or anything likely to be man-made, I think (and way too low for anything metallic). So, mineral nodule/concretion looks most likely and that doesn't rule out fossil/cast of something. It's also way too low for concretions in the hematite/goethite territory unless it's hollow (which they frequently are). The streak colour would be the next most helpful information.

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Roadrunner

Weight = 32.6 grams

I'll determine the specific gravity later this week once my graduated cylinder arrives.

I'm no expert, but it does look manmade, and metallic.

There are some metals that aren't easily cut with a knife.

And there are some metals that magnets don't attract.

Edited by Roadrunner

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painshill

I'm no expert, but it does look manmade, and metallic.

There are some metals that aren't easily cut with a knife.

And there are some metals that magnets don't attract.

Check back to previous post. The density appears to be in the region of 1.9g/cc. The only metal (excluding the highly reactive and unstable alkali metals) with a density below or approaching 2g/cc is magnesium at around 1.6g/cc. It for sure isn't a glob of magnesium or magnesium rich alloy.

Edited by painshill

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Auspex

The 'metallic' appearance seems to be because of its somewhat shiny surface. One of the original images, when enlarged, dispels the idea that it is metallic at all (note the chips and flakes):

post-423-0-58726300-1374678817_thumb.jpg

It is also not nearly a perfect sphere, as some of the photos suggest.

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Auspex

The tell-tale flaking at the chips (in positions that are 90 degrees from one another suggests (maybe) something of a layered composition...I cannot for this reason completely reject the possibility that it is a gigantic fossil pearl. The low density would also fit.

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Indy

Well if it's a gigantic pearl ...

I can see the National Geographic headline now

GIANT Fossil Pearl found in Back Yard

:D

Edited by Indy

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painshill

The tell-tale flaking at the chips (in positions that are 90 degrees from one another suggests (maybe) something of a layered composition...I cannot for this reason completely reject the possibility that it is a gigantic fossil pearl. The low density would also fit.

Yes... it's the layered structure that suggest concretion to me. I guess we have no non-destructive way of telling if it's hollow apart from an x-ray.

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Roz

If that were mine it would have been opened a long time ago.. Good

thing I didn't find it..

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Auspex

Yes... it's the layered structure that suggest concretion to me...

The 'flakes' appear to be thin and translucent, as if made of material of a more crystalline nature than I usually associate with the average concretion. I know I'm really reaching for clues and inspiration; my eyes are sore from squinting!

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JohnJ

It might be helpful to take additional photos in outdoor light without the flash.

I wouldn't rule out a curiously round pebble....

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painshill

I wouldn't rule out a curiously round pebble....

I would. Density!

Edited by painshill

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