Strange rock cracked open

[egarceau]

Hello! I collect rocks as a hobby, nothing serious, and have come across some rocks I just camet figure out. This first one is seemingly uninteresting from the outside, but when I cracked it open was surprised by the black powder and crystals in the center only. Thank you for trying to help me figure this out!

 

Amazon Forum Fav 👍

A History of Mining on the Kenai Peninsula, Alaska - Grab it through Amazon!

[hvacker]

You've some crystallization going on but the picture is too blurry to tell the crystal shape from here.

 

[Moesia]

Brake it again in half, take a picture and re post it. It appears to be granite from what little can be seen.

 

[huntsman53]

On the outside, the rock has a similar appearance of Kimberlite, that is if the color is correct. On the inside away from the black, it has the appearance of Gneiss.


Frank

 

[Moesia]

On the outside, the rock has a similar appearance of Kimberlite, that is if the color is correct. On the inside away from the black, it has the appearance of Gneiss.


Frank

No, in no way....

 

[DDancer]

Might wish to expand on that comment Moesia.
Huntsman has an idea though I dont agree with Kimberlite. It is morphing into something as the outer rind suggests but I have no idea myself what it is. A closer view of the reported crystallization would possibly help.

 

[Moesia]

Might wish to expand on that comment Moesia.
Huntsman has an idea though I dont agree with Kimberlite. It is morphing into something as the outer rind suggests but I have no idea myself what it is. A closer view of the reported crystallization would possibly help.

It is not morphing into anything.

 

[egarceau]

Sorry for the late response! Thank you everyone for taking the time to help figure this out! Do these pictures help at all? It could be quartz we have a lot of metamorphic rocks and quartz veins around here! I figured that at first just had never seen it in this fashion before?

 

[Golden_Crab]

Resembles Hornfel horneblende bordering a granite intrusion?

 

[Moesia]

Resembles Hornfel horneblende bordering a granite intrusion?

No. It is just a granitic rock that has been weathered a bit. She broke it on an existing crack and the rock appears to have been near to some vegetation hence the black coating. It is either granite or granodiorite, with the granite being more likely.

 

[DDancer]

Nope. The interior is fresh otherwise it would exhibit the same transformation that the rind exhibits and the rind would exhibit blackening by vegetation that your keen on Moesia. As to a granite~ yes its likely however what I'm seeing is to course grained for me to consider it granite or granitoid. The white intrusions look to be a quartzite or maybe calcite a hardness test would help. Morph simply means to transform as many materials do when exposed to the elements and thats what has me questioning its composition. The morphing in the rind is pretty deep in some areas so its a porous material. Looks more like an igneous material than anything else.

Golden Crabs idea does not fit for me either as the material is to coarse and does not demonstrate any layering or uniformity often associated with Hornfel but it is a good guess in my opinion.

Sorry but without the sample in hand there is not much I can say beyond it being an interesting specimen. Mayhap one of our other members more familiar with metamorphic and gensis materials will recognize it.

 

[Moesia]

Nope. The interior is fresh otherwise it would exhibit the same transformation that the rind exhibits and the rind would exhibit blackening by vegetation that your keen on Moesia. As to a granite~ yes its likely however what I'm seeing is to course grained for me to consider it granite or granitoid. The white intrusions look to be a quartzite or maybe calcite a hardness test would help. Morph simply means to transform as many materials do when exposed to the elements and thats what has me questioning its composition. The morphing in the rind is pretty deep in some areas so its a porous material. Looks more like an igneous material than anything else.

Golden Crabs idea does not fit for me either as the material is to coarse and does not demonstrate any layering or uniformity often associated with Hornfel but it is a good guess in my opinion.

Sorry but without the sample in hand there is not much I can say beyond it being an interesting specimen. Mayhap one of our other members more familiar with metamorphic and gensis materials will recognize it.

Stop being wrong...

 

[DDancer]

Moesia everyone has a right to their opinions but they do not have a right to disparage others. Back your thoughts up with solid information or just sit out of the conversation. If you can demonstrate what is wrong then do so. I for one dont have patience for flame.

 

[Moesia]

Moesia everyone has a right to their opinions but they do not have a right to disparage others. Back your thoughts up with solid information or just sit out of the conversation. If you can demonstrate what is wrong then do so. I for one dont have patience for flame.

What flame?

 

[Moesia]

Apologies to anyone insulted by my posts in anytime, it was not my desire. I shall refrain from posting such blunt replies in the future, it is not my desire to drive anyone off. The user that reproached me in the up post has had a valid reason for doing so. Once again apologies to all.

 

[Eu_citzen]

What she broke open could be a former crack, with some precipitated black mineral. (Sulphide? Oxide?)
That would explain the confusing look we're seeing here.
We can see some un-altered rock in the bottom right section of the latest photos.

Considering the feldspars not to elongated look (as is typical of Plagioclase - mafic rocks) I'd hazard a guess and say granitoid.

 

[Mrdigz]

I agree with DDancer about the ID of rock.

 

[DDancer]

No worries Moesia. What lite my ire was a double post *since deleted, thank you* on my being wrong. That is flame to me. I've got no problem, and actually invite correction, for being wrong however at the time I could not ignore the double post nor do I ignore the statement that I am wrong. Complete thoughts. I made my statement rather plain and agree that it is reactionary however I stand by my point. Express a complete thought or just sit it out till you can. Not like I'm always here nor do I have tons of time nor do I wish to comment on everything I see here. Heck I left this thread alone for a long time waiting to see other opinions than mine, and see if they agreed with my thinking or not. Its a group effort in my thought and not something I wish to dominate. Just share in and learn. Think we are square on that myself. You still owe me an explanation on why I'm wrong. Nuff said.

EU I can understand the though of a mafic type stone but I dont see the feldspar and the break appears fresh. The rind suggests granitoid to however it appears greening in the rind and other similarly colored dark spots on the outside suggest the interior coloration is true. It also appears to be fairly porous. High sulfide does not generally lend to greens however manganese will and thats not typical to mafic or most granatiods that I'm aware off. Might be missing something there but thats my line of thought.

 

[Eu_citzen]

DD, The yellowish-white small grains are likely the feldspar. They, to me, indicate a more granitoid composition.
The greening might be due to manganese as you say. We have LOTS of manganese locally, in granite country.

 

[egarceau]

Thank you everyone for taking the time to respond with your educated guesses on what this rock could be! I know it must be tough without being able to actually see and hold it! There is certainly the possibility some other material entered in a crack, but i'm thinking it's got to be something else (the break seemed "fresh"). It could most definitely be of granitoid composition as I believe we do have rocks of that nature around here! I'm still hoping someone happens to come across this and has seen something like this and can help me more with the identification! Until then I still have many other rocks to play around with! Thank you again!