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Can someone shed some light on this object?


Jackalope122

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Hello, I was hoping someone more experienced could shed some light on whether this object is anything of interest or if it's something man-made like a bead that happens to look like a natural formation. It was found in Rockford, IA at the fossil quarry, so Devonian if it's actually something fossilized. Is it possible it's a mineral formation of some kind? It's roughly 4mm x 4mm and non-magnetic. It seems to be well embedded in the rock. Thanks for your time!

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It's a pretty nicely formed crystal, possibly a garnet.  You'd have to check hardness and some other things I'm not very familiar with to confirm the mineral.  Niceone!

 

Don

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thats a beautiful little gem. Probably not fossil, but a really cool geological piece! Also welcome to the forum. :)  

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I agree with FossilDAWG...looks like a garnet to me too!  Very NICE!  The only thing that bothers me is that you say it is non-magnetic.  Did you use a STRONG magnet or just a simple household magnet?

 

-Joe

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I have a 150lb pull retrieval magnet from harbor freight and it shows no signs of attraction that I can see. Should it if it were a garnet? I only checked in the first place because of the rust color, I had no idea garnets should be magnetic. I'm not well versed in geology, as you can probably tell lol 

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Probably a pyrite or altered pyrite (limonite?). Pyrite is common in limestones. Because it was found in a fossiliferous limestone quarry a garnet is unlikely since garnet is an igneous or metamorphic mineral. The fossils would be destroyed if there were enough metamorphism to form a garnet.

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Garnets generally ARE metamorphic, which implies high temperature and pressure as DPS Ammonite says...but don't know about the condition of the fossils in your quarry because I don't SEE any fossils!  If it was pyrite (FeS2), I would certainly expect it to be attracted by a strong magnet!  I have never personally seen pyrite with crystals shaped like that (they are usually cuboidal or a variation on that theme) but I did read somewhere that pyrite can form dodecahedral crystals under certain circumstances.  And no...not all garnets are attracted to magnets!

 

-Joe

 

 

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This could well be pyrite (or have been - now some form of iron oxide?). The truncated corners on the cubes are pretty common for pyrite, and are called cuboctahedra; imagine continuing that process, and you end up with an octahedron, which is the other common growth form (besides framboids). Nice example!

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Welcome to TFF!

I agree with a pyrite crystal altered into iron oxide (goethite or hematite).

The only iron mineral that is magnetic is magnetite.

With the advent of super magnets some other minerals are "magnetic" including a few varieties of garnet that have a high iron content.

Darwin said: " Man sprang from monkeys."

Will Rogers said: " Some of them didn't spring far enough."

 

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49 minutes ago, Fruitbat said:

Garnets generally ARE metamorphic, which implies high temperature and pressure as DPS Ammonite says...but don't know about the condition of the fossils in your quarry because I don't SEE any fossils!  If it was pyrite (FeS2), I would certainly expect it to be attracted by a strong magnet!  I have never personally seen pyrite with crystals shaped like that (they are usually cuboidal or a variation on that theme) but I did read somewhere that pyrite can form dodecahedral crystals under certain circumstances.  And no...not all garnets are attracted to magnets!

 

-Joe

 

 

The fossils at the Rockford fossil quarry are generally well preserved, at least in my limited experience. Thanks everyone for taking the time to comment, I really appreciate it!

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garnet imo, oxyded garnet, theones we have here in britanny (and we have a lot) nearly always have that brownish aspect due to oxydation.

 

like those for instance : 3237463771_1_9_ugWVqIm8.jpg

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I’m also in the limonite (or other iron oxide) camp. Is a wierd shape though, wonder if it replaced a crystal of some sort, kinda like how pyrite replaces asbestos in tigers eye but with a different mineral.

“...whilst this planet has gone cycling on according to the fixed law of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been and are being evolved.” ~ Charles Darwin

Happy hunting,

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2 hours ago, elcoincoin said:

, oxyded garnet, theones we have here in britanny (and we have a lot) nearly always have that brownish aspect due to oxydation.

Garnets do not oxidize. They can be a dark brown / rust color, but that is from the elemental traces in the structure.

They also take a lot of heat and pressure to form, which is not found in sedimentary rock.

Darwin said: " Man sprang from monkeys."

Will Rogers said: " Some of them didn't spring far enough."

 

My Fossil collection - My Mineral collection

My favorite thread on TFF.

 

 

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I'm fine with some variety of pyrite.  I suggested maybe garnet because of the crystal shape, but I did say tests would be needed to ID the mineral conclusively.  I don't know the geology of the Rockford quarry, but I have collected at limestone quarries (such as the ones around Montreal) where igneous dikes and sills are present and contain a spectacular array of unusual minerals.

 

Don

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If it's in limestone, and it appears to be, then +1 for oxidized pyrite. 

It's a nice piece, very interesting! :)

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