Jackalope122 Posted May 15, 2018 Share Posted May 15, 2018 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! Link to comment Share on other sites More sharing options...
FossilDAWG Posted May 15, 2018 Share Posted May 15, 2018 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 4 Link to comment Share on other sites More sharing options...
Bone guy Posted May 15, 2018 Share Posted May 15, 2018 thats a beautiful little gem. Probably not fossil, but a really cool geological piece! Also welcome to the forum. 1 Link to comment Share on other sites More sharing options...
Jackalope122 Posted May 15, 2018 Author Share Posted May 15, 2018 Thanks for the help, and the welcome! I appreciate it! Link to comment Share on other sites More sharing options...
Fruitbat Posted May 15, 2018 Share Posted May 15, 2018 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 1 Illigitimati non carborundum Fruitbat's PDF Library Link to comment Share on other sites More sharing options...
Jackalope122 Posted May 15, 2018 Author Share Posted May 15, 2018 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 Link to comment Share on other sites More sharing options...
DPS Ammonite Posted May 15, 2018 Share Posted May 15, 2018 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. 8 My goal is to leave no stone or fossil unturned. See my Arizona Paleontology Guide link The best single resource for Arizona paleontology anywhere. Link to comment Share on other sites More sharing options...
Jackalope122 Posted May 15, 2018 Author Share Posted May 15, 2018 Very cool, thanks! Link to comment Share on other sites More sharing options...
Fruitbat Posted May 15, 2018 Share Posted May 15, 2018 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 2 Illigitimati non carborundum Fruitbat's PDF Library Link to comment Share on other sites More sharing options...
Spongy Joe Posted May 15, 2018 Share Posted May 15, 2018 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! 5 Link to comment Share on other sites More sharing options...
ynot Posted May 15, 2018 Share Posted May 15, 2018 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. 4 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. Link to comment Share on other sites More sharing options...
Jackalope122 Posted May 15, 2018 Author Share Posted May 15, 2018 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! Link to comment Share on other sites More sharing options...
Pemphix Posted May 15, 2018 Share Posted May 15, 2018 No garnet imo. It's oxydized pyrite (therefore non-magnetic) grown as interpenetration twin - i think it is Kuboktaeder, Combination of {100} and {111} see for example here: https://de.wikipedia.org/wiki/Pyrit 1 Link to comment Share on other sites More sharing options...
elcoincoin Posted May 15, 2018 Share Posted May 15, 2018 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 : Link to comment Share on other sites More sharing options...
Miocene_Mason Posted May 15, 2018 Share Posted May 15, 2018 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. 1 “...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, Mason Link to comment Share on other sites More sharing options...
ynot Posted May 15, 2018 Share Posted May 15, 2018 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. 2 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. Link to comment Share on other sites More sharing options...
Plax Posted May 15, 2018 Share Posted May 15, 2018 DPS ammonite has it right in my opinion. Link to comment Share on other sites More sharing options...
FossilDAWG Posted May 15, 2018 Share Posted May 15, 2018 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 3 Link to comment Share on other sites More sharing options...
Tidgy's Dad Posted May 15, 2018 Share Posted May 15, 2018 If it's in limestone, and it appears to be, then +1 for oxidized pyrite. It's a nice piece, very interesting! 1 Life's Good! Tortoise Friend. Link to comment Share on other sites More sharing options...
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