Very Strange and Unique 'Rock' I Found and Need Help Identifying

a reply to: westcoast

Howdy,

Thanks for the response. From what I've heard so far, it sounds like you've either got some heavily oxidized pyrite grains (fools gold, heavy stuff as it has iron in the formula. Often not very magnetic) or some garnets, depending on colouration and shape. Garnets should show a hexagon in outline, not usually square. From the close up picture, it certainly looks like you might have both hexagons and squares, meaning you might actually have both garnets and pyrite. Could you confirm that they shiny grains are actually two different things?

If the dark, reddish, very reflective grains are garnet, you're likely looking at a metamorphic rock (which might be the case, considering the banding of minerals, which might be foliation). In this case, it might be a gneiss, but it could also be a cooked argillaceous(clay-ey) sandstone, making it perhaps a quartzite. It looked a lot like a metapelite (pelite meaning shale-like stone), but if it isn't flakey and it is very hard in the lighter orangish areas, that might not be a good fit.

Honestly though, I do apologize for not being more helpful. I can say with some certainty that you're dealing with iron pyrite (golden, shiny, heavy, and square grains... some oxidized to reds, purples, browns, and oranges...), but that's about all I'm confident about.

Sincere regards,
Hydeman

a reply to: hydeman11


Thank you again for your comments! I will search all of those types and compare...but I think I might have figured it out and would love your opinion.

I'm thinking it might be a fulgurite. (or fossilized fulgurite, if that's possible?) I found this image, which looks exactly like it!!



SOURCE

It seems to have so many of the characteristics. If it is, I'm wondering what was stuck into it!

a reply to: westcoast

Howdy,

I've not had the pleasure of examining too many fulgurites, to be honest, so I could very well be incorrect about this, but...

The presence of sulphides (pyrite in this case) is usually an indicator of hydrothermal activity. Sulphides do also occur in igneous rocks as an accessory. The important thing to remember about pyrite, though, is that it is... unstable in oxidizing environments. It weathers (rusts) rather quickly (can turn red, brown, purple...). In fact, pyrite is the main culprit in the problem of acid mine drainage, as it literally weathers to sulfuric acid (and it does so relatively quickly...). For this reason I find it unlikely that so many large grains of pyrite would be associated in a sandy environment in which lightning could strike and create a fulgurite.

Now, an ancient fulgurite might (hypothetically speaking) have the time to be buried, subjected to hydrothermal activity, have sulphides deposit in the pore spaces, and then be brought back to the surface, but I'm not sure how porous fulgurites can be, and it certainly looks like you have a lot of pyrite grains.

I'm sorry to say that I don't think it is a fulgurite, but I cannot be certain. If you know of any geologists local to your area who could examine it, that would be the way to go. Nothing quite like seeing with your own eyes and feeling with your own hands, you know?

Sincere regards,
Hydeman

a reply to: hydeman11

Thanks again!

I searched those rocks and neither of them look like this specimen. I got a closer pic of it that I can blow up (funny how my cell phone can act like a sort of magnifying glass). The specs are, indeed, hexagonal in shape. I don't see any squares, but there are certainly different colors there. Black, red, gold, silver and opalish. It sparkles in the light now that I have cleaned it more.

I used its edge to scratch at a bottle of Smirnoff (yumm) and it DID scratch it, but I don't know if all of the stuff sticking out of it would. I want to make it clear, too, that the surrounding 'rock' around the garnets, or whatever they are, isn't soft either. I think I am just cleaning off a whole lot of years worth of dirt and maybe rust. As I am cleaning it, it does have more of a rust smell.

My son suggested that I lick it, which I did. it is NOT salty. Given that I am currently writing a scifi trilogy about a virus released from a meteor...that might not have been a good idea.

a reply to: westcoast

Howdy,

Ah, hexagonal grains. I should mention, as I have thus far failed to, that pyrite can sometimes appear hexagonal in cross-section, too. It has a nasty habit of twinning and can grow in dodecahedron.
www.mindat.org...

Compared to a common garnet (well, common species, anyway)...
www.mindat.org...

It can be hard to tell the two apart from a picture, but if you see the striations (grooved lines) on the crystal surfaces, it is almost assuredly pyrite. Garnet will usually appear cracked. This is itself a useful test, as garnet fractures and produces a very irregular surface, but the inside colours will remain consistent. Weathered pyrite will fracture similarly, but it would leave a blackish-grey dust (iron) or soft reddish powder if the mineral were completely replaced. This is why I asked if you would break a piece off to expose a fresher surface.

One of the big issues with pyrite grains is that they do weather quickly, producing sulfuric acid and leaving behind oxidized iron (rust indeed ). The iron can coat the mineral grains, pervasively (into the rock) or on an external surface, leaving rocks an orange-brown shade which they might not otherwise be.

A glass bottle is about 5-6 on Moh's hardness scale, so that is consistent with both pyrite and garnet, as well as many other minerals. On the bright side, you ruled out a lot of the softer minerals (like fluorite, for example).

If the matrix (the material that isn't the shiny hexagonal-ish grains) is indeed hard material, then it is very likely feldspar or quartz (quartz also grows hexagonal crystals, and would also scratch glass...), which would likely indicate granite or sandstone (meta or not). Perhaps an orange stained arkosic sandstone would be a good fit?

As for licking rocks... In one of my mineralogy exams (well, one in particular, all of them after), we were tasked with identifying evaporites, which are minerals formed by evaporation of mineral rich waters. Table salt (halite) looks, acts, and feels the same as a salt known as sylvite. The only way to distinguish them is by the rather... uniquely bitter taste of the sylvite compared to halite. >.> It's rarely a good idea to lick rocks, but sometimes it helps, unless it is coated in space virus.

Good luck with the sci-fi, by the way. I'm a big fan of the genre.

Sincere regards,
Hydeman

a reply to: hydeman11

Thank you! I'll let you know if I develop any symptoms.

Here is a cropped close-up of the surface.


Its hard to see it without the option to zoom in, but because only one side of the surface is refracting the light, it makes it appear square, when it isn't. They seem to all be hexagonal. But...when I scratched the glass, it left a dark residue, which sounds more like pyrite, but I guess that could have been dirt, too.

It's a petrified dinosaur turd!

a reply to: w8tn4it

Naw it's two calcified bufo marinus toads doing the nasty

I was finally able to get it into a rock/gem store. He thinks that it's a really old deposit of iron pyrite and the rock that it was worn away after likely millions of years to leave to compressed iron behind.

kind cool...

a reply to: westcoast

Howdy,

Congrats on the identification, and thanks for the update. It is a lovely sulphide specimen and it would look wonderful in anyone's collection.

Sincere regards,
Hydeman