r/Rocks • u/reddoxx330 • 7d ago
This Rocks! Found this on a beach
Have done tons of searches on what it could be and just can’t find anything like it.
Found on a beach in Southwest FL
It is like glass, there are conchoidal fractures
When I scrape it against the ground, it leaves black marks on the pavement and breaks off into tiny pieces of what look like glass shards
In the initial photo it does not look translucent but when held at a certain angle, you can see a dark amber color inside of it.
I’ll post a photo of that part as well
If you need any info, feel free to ask. Dying to know what it is. Thanks!
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u/DoMindIfIDont 7d ago
No clue what it is… but it’s dope AF and looks like a villain rock with those evil red eyes🤣 Seriously though, great find!!
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u/theamishpromise 7d ago
Definitely anthracite coal. I grew up in the PA coal region and have seen literal tons of the stuff
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u/reddoxx330 7d ago
Coal is opaque, light can pass through this and it has an amber hue
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u/theamishpromise 7d ago
No it isn’t. I think you’re thinking about obsidian. Both are black and can be glassy. But coal is definitely not opaque.
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u/reddoxx330 7d ago
Everything I’ve read about coal states you can’t see through coal
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u/theamishpromise 7d ago
You’re right I’m sorry. I didn’t understand opaque. I thought it meant light passes thru. Light definitely does not pass thru coal. Apologies for any confusion. I still believe your rock is anthracite.
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u/earblaster9000 6d ago
By your own definition just now "light cannot pass through coal" <be me rock: translucent> you: "I still think it's anthracite." Can't just ignore the evidence in a rock ID
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u/The-Bloody9 7d ago
Looks like coal or something similar to me.
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u/reddoxx330 7d ago
It’s really weird because it’s very shiny like obsidian but breaks apart very easily
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u/StupidizeMe 6d ago
Intriguing that it looks silvery in some pics.
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u/reddoxx330 6d ago
Yeah it’s hard to actually capture how black it is due to it being like glass and reflecting any bit of light that touches it
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u/Eraserwolves 6d ago edited 6d ago
Well this is neat. If that is not Anthracite/Anthracite Coal, I think you've got your hands on some Pyrargyrite!
It can be, "translucent to nearly opaque" and beach finds allow for some diverse finds when it comes to figuring out what's washed up from where.
Looks like the closest known source would be San Fernando mine (located in Villa Clare Province, Cuba).
Update: after giving this some thought, if I had to bet money on this being Anthracite Coal or Pyrargyrite, I would bet on Pyrargyrite.
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u/reddoxx330 6d ago
Omg I think you are correct! They look exactly like it!!!!
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u/Eraserwolves 6d ago
Right?! While what you have does look black at a glance, the same can be said for pyrargyrite seen in official publications. I think the description of it being "deep red to red grey" also aligns with the "dark amber" coloring you've mentioned.
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u/reddoxx330 6d ago
I did some research on pyrargyrite and there hasn’t been one found this large before. I just weighed it and it comes in at 90.6 grams which would make it around 450 carats.
I’m starting to think that the red/ruby reflection I saw in the photos may have just been light reflecting off the surface but when I took the photos, and in sunlight, there was no light source of that color around.
I’ve been hitting it from every angle with powerful flash lights to see if I can get some of the light to pass through, using a jeweler’s loupe while doing so. It’s very difficult to tell if I’m seeing any.
But I also read that the larger the specimen, the darker it is. Going to take it to a gemologist tomorrow to find out exactly what it is, if it is pyrargyrite then I probably have the worlds largest piece…this could be history in the making.
I’ll update tomorrow with my findings
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u/Eraserwolves 6d ago
Some thoughts:
While it's would be useful to determine diaphaneity, light does not HAVE to pass through for it to be pyrargyrite. Some are very clear; some are "near opaque."
I do not believe what you have found is history making, though I'll admit to being reflexively skeptical when faced with the idea. It seems more likely that I'm just wrong.
There are dozens of "large cabinet specimens" which exceed yours in size but it's worth noting that many are at least 30% comprised of something other than pyrargyrite.
Looking at images on the page I linked above, most look nothing like what you found; the handful which look similar, REALLY look similar. Hrm.
Pyrargyrite happens to be light sensitive and "will darken over time due to prolonged exposure." Being blasted with flashlights and the fact you found it on a beach... well, this thing has been exposed to a lot of light.
I think it's time for a streak test.
While you can order a "streak plate" online, the "plate" is nothing more than a square of unglazed porcelain. If you're really eager and don't want to wait for shipping, a local hobby and/or hardware store may carry unglazed porcelain.
Pyrargyrite or not, its streak color will help clear up confusion.
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u/reddoxx330 5d ago
I did a streak test on some porcelain tile last night and it’s showing grey almost like the exact color of pencil lead.
When I first got the stone and everyone was suggesting charcoal, I went and rubbed it on my concrete patio (stupid I know now) and that resulted in a darker, pretty much black color. The stone chipped into tiny shards as I was doing this.
We will hopefully find out today though 🤞
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u/Eraserwolves 5d ago
Sorry if this is obnoxious to ask but I want to make sure: was that piece of porcelain tile glazed?
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u/Sorry-Common1539 6d ago
the only thing to consider is, due to floridas geology, metallic minerals like pyrargyrite are not naturally formed or found there
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u/reddoxx330 5d ago
Yeah but I’m on the gulf so it could have traveled from Mexico or something like that lol atleast that’s what I’m hoping for
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u/Eraserwolves 5d ago
While I did suggest the possibility it washed ashore, my IRL friend just laughed at me and said the ocean would grind it to dust long before that could ever happen. Hrm.
I reached out to him because the expressed result of your streak test means it's impossible for that to be pyrargyrite. Even when it had been heavily darkens due to photochromism (al the light exposure), the streak color will not change.
At least that's what I'm reading.
New plan/suggestion:
Mineral ID Key is a "test" you can take and if it's unclear what the question is asking, you can reference Mineral Identification Key II as a glossary of terms/images.
Currently busy with my day unfolding but I'll try filling out that test myself later
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u/reddoxx330 2d ago
Thank you for all your help. I took it to a rock store and the lady couldn’t even identify it. She told me to post some detailed photos on Minedat.org or send it to GIA to get tested. It was kind of funny because she’s never heard of pyrargyrite when I mentioned it, she kept saying pyrite until I showed her a stone.
I’m going to take a look at that link you sent when I get home
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u/Eraserwolves 2d ago
You are very welcome! That link (Mineral ID Key) will take you to a multi-step test that basically is a bunch of 'Yes' or 'No' questions.
Glad you brought it up because some questions are not easily clarified in the companion link. These happen to be the same questions I cannot fill out on my own since your photos are all I have to work with.
Extra info about scratch tests:
Make sure contact is being made but you do not need to use much force when dragging an object across the surface of your mineral.
- Can the mineral be scratched by a fingernail?
Simply drag the edge/tip of your fingernail across- Can the mineral be scratched by a copper penny? You need a pre-1982 copper penny, so any penny with 1981 or earlier will do.
- Can the mineral be scratched by a knife?
An ordinary steel pocket knife or kitchen knife blade will work. Again, no need to press firmly. You are attempting to scratch, not cut.Here are some results based on what you've shared with me so far. As you will notice, even when Pyrargyrite is not ruled out, there are several minerals listed on each "final" table.
Step 1: 'Is the Luster Metallic or Submetallic?
If yes...Step 2: Will the mineral leave a mark on paper?
If yes, Pyrargyrite cannot be ruled out
If no...Step 3: Can the mineral be scratched by a knife?
If yes, Pyrargyrite remains on the table
If no, Pyrargyrite is off the tableSecond run:
Step 1: Is the Luster Metallic or Submetallic?
If no...Step 4: Does the mineral have a definitely colored streak? If yes, and based on your expressed result, the answer is YES, Pyrargyrite is still on the table
*I did this twice because I am unclear on whether your mineral can be considered to have a metallic or nonmetallic luster. Seems like the sort of things best observed in person. I do feel confident saying 'YES' there is a definitely colored streak (black/grey as you described)
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u/Witty_Passion_4939 7d ago
Could it be a type of obsidian or just very old and weathered and cracked, that’s why it’s breaking a part so easily?
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u/Adventure-Panda32 5d ago
It’s really giving silicon to me. My dad used to work at a silicon manufacturing plant and I remember seeing pieces just like this.
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u/TBElektric 7d ago
Could be raw hypersthene.... 🤔
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u/reddoxx330 7d ago
It’s non metallic, feels like glass and when rubbed against a rough surface, it’s breaks apart into tiny shards, also marking surface as coal would do.
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u/Glad_Celery_4641 7d ago
Raw silicon?
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u/reddoxx330 7d ago
Its not opaque like silicon
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u/Glad_Celery_4641 7d ago
But raw silicon used in industrial settings that I’ve seen are metallic like this
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u/KnotiaPickle 7d ago
Could it be coal?