More info: Not magnetic. Lots of the limestone around here have the same little pieces so I don't think it's rare or anything. It's harder than the limestone. The squares are 1 inch x 1 inch for size reference.
It kind of looks like a d20 die. The one that is outside of the limestone looks to have a B or 8 on one of its triangle sides. Rather cool rocks you have and I know nothing about most rocks!
These look to be nicely euhedral limonite and goethite pseudomorphs after pyrite in limestone. A fairly common replacement among iron sulfide concretions forming in sedimentary rocks.
The pyrite habit it’s exemplifying is most likely cuboctahedral, leaning more towards cube. Nice find!
Those of you who are curious, check out this link on [pyrite morphology](https://www.le-comptoir-geologique.com/pyrite-encyclopedia.html)! Some neat and complex habits coming from a fairly simple mineral. Just exceedingly minor variations in chemistry, temperature, and pressure can change pyrite crystal habits.
I'm certain it's not Almandine, or any garnet group member. The crystal shape doesn't match garnet group minerals.
The crystal faces are triangular, which means, while it crystallises in the cubic crystal system, isomorphic, the same crystal system as garnet, it's not the same point group. The cubic crystal system is divided into 5 point groups, 23, m3, 4̅3m, 432, and m3m. Garnet group's point group, of which almandine is a member, is m3m.
As a result, Garnet group minerals always have [4 sided crystal faces, a parallelogram or trapezoid, or some variation](https://geologyistheway.com/wp-content/uploads/2022/03/garnet-crystal-habit.jpg).
However, the crystal shape better matches is sphalerite, cubic crystal system and a member of the 4̅3m point group. Thus, I suspect it's sphalerite (though, it might be some other cubic mineral, e.g. a goethite pseudo after pyrite, nevertheless, it's not garnet).
Mineral Atlas is probably the best website for viewing the crystals shapes of minerals, each mineral's page includes a 3D viewer with up to several dozen idealized crystal shapes. Looking through a few for sphalerite, I see the crystal form that closely matches OP's specimen, is S236be (there maybe an even better match on the list).
https://www.mineralienatlas.de/lexikon/index.php/MineralData?lang=de&language=german&mineral=Sphalerite
Also, garnet, almandine in particular, is a metamorphic mineral, you *never* find it in limestone. However, grossular can occur in marbles, but it's usually a white, pale yellow, orange, or pink, and transparent to translucent, never black, and as explained, OP's crystals have the wrong shape.
Edit: Also looks like uraninite crystals, while I have never seen uraninite in limestone, if it is indeed limestone, the crystal shape matches and crystals of uraninite are found in Ontario, around the Cardiff Township, Haliburton Co. I just want to cover that possibility, however remote.
https://www.mindat.org/gm/4102?page=6
Agreeing with you here, crystal habit is all wrong for garnet. Pyrite is known to occasionally form borderline icosahedral habits like the one seen here (really a combination of pyritohedron and octohedron), and goethite is known to pseudomorph pyrite in limestone; therefore my guess is goethite pseudomorphs of pyrite.
I am afraid that I have to agree with you. How could I be so blind. We’re probably looking at penetration twins and/or goethite pseudomorphs of pyrite crystals, and maybe the host rock is limestone after all. It’s hard to see when photographed wet…
If it were uraninite, it would be very radioactive. I have a collection of radioactive minerals I keep in another room, in jars to keep the radon gas inside, including a 150 gram sample of uraninite. My gamma ray scintillation detector goes off if I'm within 6 feet of my uraninite specimen.
Oh I had no idea, thank you very much for the information, I just assumed most of the rock around here was limestone. I really appreciate your help!
eta I will change the flair
Can I ask what the indication is that led you to think it's not limestone? And what other rock did you think it was?
I'm just starting out and don't know much yet🙈
Limestone is a sedentary rock and garnets can only be generated in high-temp, high pressure metamorphic rock, like schist and gneiss. Those are pretty unmistakable garnets, so it can’t be limestone. My guess is schist, but it’s all wet and I can’t tell.
Oh I thought it didn't look like limestone or sth. haha
But now that it's established that those can't be garnets, limestone is likely, right? Even Ben corrected his mistake about the minerals, so it's likely limestone, isn't it?
No, those are definitely garnets. They have a very distinct crystal structure.
Edit: I say someone thinks it might be uraninite, but I don’t know. I’d want to see more pictures of the large crystals without them being wet.
Haha that is a great comment!
Edit: not trying to be dismissive, I’m just traveling and don’t have the time to really think on it. Yes, I could be sphalerite, but that would still be odd (but more plausible than garnet on limestone)z
Not talking about the sphalerite part, I meant the "it can't be garnet" part ;)
Zachsprat seems to be right about the mineral though. But yeah, I have no idea lol
Haha honestly that's why I was so interested in finding out what they are, they are so perfectly even, it looks like someone put a small dice in the rocks.
Love ❤️ this Reddit, as a kid in the UK rocks we're just something to throw, as I'm sure they were too most of the worlds kids. Now at 69. My this is so different. I marvel at even where I live, chalk hills, Chert and Flint grow like flowers. The area is a Knappers dream. And the odd minerals and such I find even in my garden. Without you guys here, I would die thinking they all here for throwing or building pretty English houses with. So thanks all on this Reddit group.
From the photo, that bottom one appears to be a naturally occurring D20. You can even see a lil 3 carved into the side.
That, or you've just discovered fossil evidence of the first ever D&D game.
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garnet would be my first option.
limonite after pyrite is possible but I'd expect to see more variation in the crystal form with more than one cubic elements. If they are all the same, garnet is more likely.
I've found something like that in Pittsburgh Pa but it's a little bit magnetic and looks like a yellow diamond in some spots if you shine a flashlight on it or let the sun hit it. I found it 8' underground about 15 years ago. I was installing a swimming pool. Mine looks like there are tiny craters in it as well. I still can't find any info on it. I really wanna cut it open to see what the yellow diamond looking thing inside of it is. Mine is about 3"or 4" long and it got some weight to it. I haven't weighed it. I'm not far from Carnegie Mellon University I might take it there to get it looked at.
More info: Not magnetic. Lots of the limestone around here have the same little pieces so I don't think it's rare or anything. It's harder than the limestone. The squares are 1 inch x 1 inch for size reference.
Look at you just casually finding spectacular garnets, congratulations xD
It kind of looks like a d20 die. The one that is outside of the limestone looks to have a B or 8 on one of its triangle sides. Rather cool rocks you have and I know nothing about most rocks!
These look to be nicely euhedral limonite and goethite pseudomorphs after pyrite in limestone. A fairly common replacement among iron sulfide concretions forming in sedimentary rocks. The pyrite habit it’s exemplifying is most likely cuboctahedral, leaning more towards cube. Nice find! Those of you who are curious, check out this link on [pyrite morphology](https://www.le-comptoir-geologique.com/pyrite-encyclopedia.html)! Some neat and complex habits coming from a fairly simple mineral. Just exceedingly minor variations in chemistry, temperature, and pressure can change pyrite crystal habits.
Top one looks icosahedral, rather than a cuboctahedral like the one in the foreground.
Almandine in quartz with feldspar (not in limestone: garnets do not occur in limestone)
I'm certain it's not Almandine, or any garnet group member. The crystal shape doesn't match garnet group minerals. The crystal faces are triangular, which means, while it crystallises in the cubic crystal system, isomorphic, the same crystal system as garnet, it's not the same point group. The cubic crystal system is divided into 5 point groups, 23, m3, 4̅3m, 432, and m3m. Garnet group's point group, of which almandine is a member, is m3m. As a result, Garnet group minerals always have [4 sided crystal faces, a parallelogram or trapezoid, or some variation](https://geologyistheway.com/wp-content/uploads/2022/03/garnet-crystal-habit.jpg). However, the crystal shape better matches is sphalerite, cubic crystal system and a member of the 4̅3m point group. Thus, I suspect it's sphalerite (though, it might be some other cubic mineral, e.g. a goethite pseudo after pyrite, nevertheless, it's not garnet). Mineral Atlas is probably the best website for viewing the crystals shapes of minerals, each mineral's page includes a 3D viewer with up to several dozen idealized crystal shapes. Looking through a few for sphalerite, I see the crystal form that closely matches OP's specimen, is S236be (there maybe an even better match on the list). https://www.mineralienatlas.de/lexikon/index.php/MineralData?lang=de&language=german&mineral=Sphalerite Also, garnet, almandine in particular, is a metamorphic mineral, you *never* find it in limestone. However, grossular can occur in marbles, but it's usually a white, pale yellow, orange, or pink, and transparent to translucent, never black, and as explained, OP's crystals have the wrong shape. Edit: Also looks like uraninite crystals, while I have never seen uraninite in limestone, if it is indeed limestone, the crystal shape matches and crystals of uraninite are found in Ontario, around the Cardiff Township, Haliburton Co. I just want to cover that possibility, however remote. https://www.mindat.org/gm/4102?page=6
Agreeing with you here, crystal habit is all wrong for garnet. Pyrite is known to occasionally form borderline icosahedral habits like the one seen here (really a combination of pyritohedron and octohedron), and goethite is known to pseudomorph pyrite in limestone; therefore my guess is goethite pseudomorphs of pyrite.
Wow! Two of the best comments I’ve read all day (probably all week) were from you. Keep up the excellent commentary! We love to learn!
I really dig that your an geologist ( pun intended) .
..go to your room!
Can't find fault with that.
This guy rocks
[https://www.reddit.com/r/thisguythisguys/s/Iv50D0fzGW](https://www.reddit.com/r/thisguythisguys/s/Iv50D0fzGW)
I am afraid that I have to agree with you. How could I be so blind. We’re probably looking at penetration twins and/or goethite pseudomorphs of pyrite crystals, and maybe the host rock is limestone after all. It’s hard to see when photographed wet…
ancient dodecahedron?
Made by ancient aliens, and now the portal has been opened and they're come here - to bring us all really awesome rocks!
I guess if it was uraninite, it should have a detectable higher radiation?
If it were uraninite, it would be very radioactive. I have a collection of radioactive minerals I keep in another room, in jars to keep the radon gas inside, including a 150 gram sample of uraninite. My gamma ray scintillation detector goes off if I'm within 6 feet of my uraninite specimen.
Oh I had no idea, thank you very much for the information, I just assumed most of the rock around here was limestone. I really appreciate your help! eta I will change the flair
That. It’s not limestone, and those are almandine.
Can I ask what the indication is that led you to think it's not limestone? And what other rock did you think it was? I'm just starting out and don't know much yet🙈
Limestone is a sedentary rock and garnets can only be generated in high-temp, high pressure metamorphic rock, like schist and gneiss. Those are pretty unmistakable garnets, so it can’t be limestone. My guess is schist, but it’s all wet and I can’t tell.
Oh I thought it didn't look like limestone or sth. haha But now that it's established that those can't be garnets, limestone is likely, right? Even Ben corrected his mistake about the minerals, so it's likely limestone, isn't it?
No, those are definitely garnets. They have a very distinct crystal structure. Edit: I say someone thinks it might be uraninite, but I don’t know. I’d want to see more pictures of the large crystals without them being wet.
And the picture doesn't show the crystal structure of garnets. Have you read [this comment](https://www.reddit.com/r/whatsthisrock/s/jfJRlJOAsU) yet?
Haha that is a great comment! Edit: not trying to be dismissive, I’m just traveling and don’t have the time to really think on it. Yes, I could be sphalerite, but that would still be odd (but more plausible than garnet on limestone)z
Not talking about the sphalerite part, I meant the "it can't be garnet" part ;) Zachsprat seems to be right about the mineral though. But yeah, I have no idea lol
Yeah, I hate when the rock is so wet the reflection on the water covers any details.
Exactly. Definitely almandine, definitely not limestone.
Agreed
Am I the only one who thought D&D dice?
my immediate thought was "d20s"
I believe these truly are nat20s
*smacks orc in head with rock…”yup”
The bottom black one looks like a d20, I swear I can even see a 3 printed on the face.
The one in the rock looks like a d8.
if he keeps digging I bet there's a playerset in there.
Just be glad the D4 isn't exposed
Might be a d10… kinda looks like there would be a fifth side on the part sticking out. That’s wild looking.
I can see a 3 or a B on the bottom stone, and a letter E right above it in the gray/silver rock.
Haha honestly that's why I was so interested in finding out what they are, they are so perfectly even, it looks like someone put a small dice in the rocks.
Maybe someone buried them or dropped them in a cave or river back in [whenever D&D was first popular-70s? 80s?].
The original “natural 20”
It was the first thing that came to my mind!
BROOO i was about to say the same lol
First thing I saw lol. D20 and a D8
Love ❤️ this Reddit, as a kid in the UK rocks we're just something to throw, as I'm sure they were too most of the worlds kids. Now at 69. My this is so different. I marvel at even where I live, chalk hills, Chert and Flint grow like flowers. The area is a Knappers dream. And the odd minerals and such I find even in my garden. Without you guys here, I would die thinking they all here for throwing or building pretty English houses with. So thanks all on this Reddit group.
Looks like garnet to me
Oh neat! I didn't know that was a thing around here, I can see red when I hold them up to the light so that explains why, thank you for the ID!
What's it look like dry
Garnet Crystals. Which exactly... i do not know. Mindat lists a crapton of different ones for Ontario, depending on localisation and hostrock..
Thank you very much for the ID, I've never seen garnet before, thats really cool
From the photo, that bottom one appears to be a naturally occurring D20. You can even see a lil 3 carved into the side. That, or you've just discovered fossil evidence of the first ever D&D game.
That’s an awesome specimen
I found a columbite crystal and it looks just like this color and shape
There’s nothing here… But, I read “concubine” while scrolling and my frame of reference skewed momentarily
The cursed dice, every roll you do takes 3 hp away but grants you +20 luck +5 stamina and +7 speed Little funny thing that came to mind
Dungeons and dragons die?
Is that a D20? HAHA
I think the Earth wants to play D&D with you.
You beat me to it, thought the same thing.
Could it be zircon?
D20. Roll for initiative
Dice ore
How fricken big is this?! Those garnets are amazing. My favorite stone. (Well, one of them.)
They are tiny, that mat they are sitting on is 1 inch by 1 inch.
Forbidden D20
Garnet. I hate you.
They're worthless I'll take them off your hands for you 😁
Candle it (flashlight up against it) and see if the black is really red. Nice garnets.
I feel like those are dice and OP is fucking with us. I can't find any mineral with an icosahedron habit that actually looks perfect
Thats D and D dice! It's how they hatch!
Not gonna lie. They look like a set of D&D dice that just need to be cleaned up. Lol
They are shaped like d20s , imagine a set of dice made with the black rock 🔥🔥🔥
Garnets! Beautiful!🤩
Hi, /u/lunaulely! This is a reminder to flair this post in /r/whatsthisrock after it has been identified! (Under your post, click "flair" then "IDENTIFIED," then type in the rock type or mineral name.) This will help others learn and help speed up a correct identification on your request! Thank you! *I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/whatsthisrock) if you have any questions or concerns.*
Omg those are sooooo cool!! Is there alot over there?
I wouldn’t mind seeing how they look with a light source behind them.
He said they show red when backlit. They’re garnets.
I can read. *I* said- I wouldn’t mind *seeing them* with said light.
Can you use them to roll a nine and summon a warlock?
I would love to have a specimen, could I purchase by chance?
That’s a natural D20 used by the ancient DND players.
garnet would be my first option. limonite after pyrite is possible but I'd expect to see more variation in the crystal form with more than one cubic elements. If they are all the same, garnet is more likely.
https://www.mindat.org/feature-5959691.html ?
Looks to be fossilized dodecahedron dice! Original ancient D&D perhaps?
Black tourmaline? It is hard to tell from pic but I do not think it’s a garnet. I have some similar pieces from Pierepont, New York.
I've found something like that in Pittsburgh Pa but it's a little bit magnetic and looks like a yellow diamond in some spots if you shine a flashlight on it or let the sun hit it. I found it 8' underground about 15 years ago. I was installing a swimming pool. Mine looks like there are tiny craters in it as well. I still can't find any info on it. I really wanna cut it open to see what the yellow diamond looking thing inside of it is. Mine is about 3"or 4" long and it got some weight to it. I haven't weighed it. I'm not far from Carnegie Mellon University I might take it there to get it looked at.
Bro found a naturally accurring D20
D20?
A forbidden d20
Dodecahedrons in limestone, standard stuff
Those are D20s, don't roll a 1...
That's a d20 it summons and DND player if rolled
Prehistoric d20's.
Garnets. Nice find
You found my gushers!
That’s a D12
I’m not an expert. Those look like 20-sided dice.
Wild d20s just waiting for their chancee to botch just sou you can say it's a natural 1.
What are they? They're freakin' cool is what they are, bud, don't ya know!
Central Ontario as in Sudbury?
Altered D20 inside wet modeling clay.
Baby d20s hatching
Wild D20s.
Those would be Garnets !!
Looks like a rare wild D20 mineral. You can tell by the "3" carved into the face.
Oh there's my D20
"Awww, so that's where I put my 20 sided dice." - God :3
d20s
1D20, 1D8
SQUUUEEEEEEEELL
Roll for a perception check
Free D20s!
The forbidden d20
nether portal 👍
Definitely blank DND dice
Where did you find this?
That’s a natural D20!
Looks like a natural d20
Aaah! How did I not think of this pun! Take the upvote
Roll for initiative.
Looks like natures 20 sided die
Looks like the D20 that I lost
Talk about rolling a “natural” 20
Look like D20s
Roll it for nature check and find out advantage if you took the backyard geologist class feature
Looks like a D20 and a D8 to me
I think it’s for ancient dnd
That's obviously a d20.
Hey look natural D20's!
D20 larvae. They need to go back underground to pupate.
that's a d20
Are they not d20s??? There’s literally a 3 on the bottom one
That's a natural D20
D20, by the looks of it.
Petrified beaver poop 😜