Thank you for sharing your knowledge with us 😊 I’m so happy that we can have access to this type of info from people like you who are kind enough to share the things they are passionate about and spark new interest in the subject for people. I appreciate it! Thank you for taking the time to make and share your videos with us.
Yeah I'll make my way over Georgia in a heartbeat... just kidding I'm from England and I just happened to find this haha. Now I know more about metamorphic, that huge piece you had helped my visualize the process and transformation of the original granite.
Great question Antonio, I suggest looking at many samples of the granite I’d in question. Magmatic flow structures mostly occur near pluton edges, with well formed crystal faces. If I saw consistent banding especially of potassium feldspar crystals over a wide area, and the geo map labeled the granitoid as a gneiss, I would relax and call it such. In my opinion, in the field, you are far likely to see metamorphic banding versus magmatic banding. Also, there is no substitute for reading up on the tectonics of the granitoid. Hope this helps, and THANKS for the comment!😊
Great question, Richard. With sedimentary rocks, if you see ripple marks in shale or evidence of mud cracks, you can assume you’re looking at the top. If you see cross bedding in sandstone, then you’re looking at a side view and can identify the top. But the best way in sedimentary rocks is to look at the rock formation. This will give clues as to top and bottom. With granite gneiss and other metamorphic rocks, I don’t know of a good way to tell that folks like you and I can use. Hope this helps and happy rock hunting!
Hi Abdul, Pretty sure it’s ortho because: Its Athens granite gneiss emplaced during Acadian orogeny as granite and metamorphosed during Alleghanian orogeny, and in my opinion most granite gneiss are ortho. Sediments usually end up as schists, though with anataxis they become gneisses. Just my take and hope it helps, Friend😊
Hi Cody, stripes form because high heat and high pressure of metamorphism causes potassium feldspar ( the white mineral) to leave the mineral matrix and migrate into light colored bands. This creates dark bands of biotite mica and the light feldspar bands. Hope this helps and happy rock hunting!
And yes, Cody you are right. It is related to different melting points. Potassium feldspar has a relatively low melting point, though it behaves more like plastic putty than liquid when it separates. Good detective work!
Hi Commander, thanks for watching. Granite gneiss has metamorphic banding, meaning the light colored minerals have separated from the dark minerals forming bands of light and dark that often swirl like in a cinnamon roll. Granite lacks these bands😊
@@PapaRocks Yeah, that's what you say in the video. 😆 Let me be more clear: I was hoping you would explain the difference between orthogneiss and paragneiss. Is there a way to tell them apart without involving labs and quantum physics?
Hi Commander, I know of no way to tell because the protolith is basically repelled. Context might be useful, but that’s over my geological head. Hope this helps and thanks again for watching and commenting!
Here is more. I believe ( my take only) most granite gneiss originates from granite. Why, because a sedimentary rock like shale is chock full of clay minerals that are most likely to meta into schist. Sandstone will meta into quartzite. Gray wacky could possibly meta into a gneiss, but all I have not seen it. Some geologists believe biotite gneiss is meta heatwave. I believe (maybe wrongly) that biotite gneiss has an igneous protolith (andesite/diorite) else where is the intermediate product of fractional melting. I’d love to talk more, so email me if you like: williams@warnell. uga.edu
I just take a rock, throw it up into the air and let it land on my head. If it hurts I know that rock is mean. And if it's mean it can't be gneiss. So far I haven't found any gneiss rocks. Now I find out I was using the wrong method to identify gneiss rocks? Well at least I found out how to identify mean rocks. Does anyone have an aspirin. I have a really bad head ache.
Thank you for sharing your knowledge with us 😊 I’m so happy that we can have access to this type of info from people like you who are kind enough to share the things they are passionate about and spark new interest in the subject for people. I appreciate it! Thank you for taking the time to make and share your videos with us.
Excellent, great teacher. Answered my questions and got right to it!
Yeah I'll make my way over Georgia in a heartbeat... just kidding I'm from England and I just happened to find this haha. Now I know more about metamorphic, that huge piece you had helped my visualize the process and transformation of the original granite.
Super glad!😊
Beautiful! Thank you so much! I think what I've got in front of me is slate, but I've only just started my journey.
How to differenciate a granite gneiss from a granite with magmatic foliation? Good video.
Great question Antonio,
I suggest looking at many samples of the granite I’d in question. Magmatic flow structures mostly occur near pluton edges, with well formed crystal faces. If I saw consistent banding especially of potassium feldspar crystals over a wide area, and the geo map labeled the granitoid as a gneiss, I would relax and call it such. In my opinion, in the field, you are far likely to see metamorphic banding versus magmatic banding. Also, there is no substitute for reading up on the tectonics of the granitoid. Hope this helps, and THANKS for the comment!😊
Is there any way to figure out which edge of a rock was at the top or bottom when it was formed?
Great question, Richard. With sedimentary rocks, if you see ripple marks in shale or evidence of mud cracks, you can assume you’re looking at the top. If you see cross bedding in sandstone, then you’re looking at a side view and can identify the top. But the best way in sedimentary rocks is to look at the rock formation. This will give clues as to top and bottom.
With granite gneiss and other metamorphic rocks, I don’t know of a good way to tell that folks like you and I can use. Hope this helps and happy rock hunting!
Is it ortho or para sir?
Hi Abdul, Pretty sure it’s ortho because:
Its Athens granite gneiss emplaced during Acadian orogeny as granite and metamorphosed during Alleghanian orogeny, and in my opinion most granite gneiss are ortho. Sediments usually end up as schists, though with anataxis they become gneisses. Just my take and hope it helps, Friend😊
Gneiss to know!
Sir I asking same question?the granite gneiss stone is ah magnetic or not?
Hi Antony,
No, granite gneiss is not magnetic. It does not stick to a magnet. Hope this helps and have a great day!
KC my bato ako dto nag mamagnet KC Ang isa black Ang isa parang gre
Why do the stripes form? Different melting points?
Hi Cody, stripes form because high heat and high pressure of metamorphism causes potassium feldspar ( the white mineral) to leave the mineral matrix and migrate into light colored bands. This creates dark bands of biotite mica and the light feldspar bands. Hope this helps and happy rock hunting!
And yes, Cody you are right. It is related to different melting points. Potassium feldspar has a relatively low melting point, though it behaves more like plastic putty than liquid when it separates. Good detective work!
Biotite? How about hornblende?
Thanks R for this comment!!Yes, you’re right, granite gneiss can have hornblende too. A nickel coin will scratch biotite but not hornblende.
No
Looking at the title, I was hoping you would explain how to distinguish granite gneiss from non granite gneiss..... still, a very good explanation.
Hi Commander, thanks for watching. Granite gneiss has metamorphic banding, meaning the light colored minerals have separated from the dark minerals forming bands of light and dark that often swirl like in a cinnamon roll. Granite lacks these bands😊
@@PapaRocks Yeah, that's what you say in the video. 😆 Let me be more clear: I was hoping you would explain the difference between orthogneiss and paragneiss. Is there a way to tell them apart without involving labs and quantum physics?
Hi Commander, I know of no way to tell because the protolith is basically repelled. Context might be useful, but that’s over my geological head. Hope this helps and thanks again for watching and commenting!
Remelted is the word, not repelled!😆
Here is more. I believe ( my take only) most granite gneiss originates from granite. Why, because a sedimentary rock like shale is chock full of clay minerals that are most likely to meta into schist. Sandstone will meta into quartzite. Gray wacky could possibly meta into a gneiss, but all I have not seen it. Some geologists believe biotite gneiss is meta heatwave. I believe (maybe wrongly) that biotite gneiss has an igneous protolith (andesite/diorite) else where is the intermediate product of fractional melting.
I’d love to talk more, so email me if you like:
williams@warnell. uga.edu
Granitic Gneiss.
I would never take gneiss for granite..
😊😊😊
I just take a rock, throw it up into the air and let it land on my head. If it hurts I know that rock is mean. And if it's mean it can't be gneiss. So far I haven't found any gneiss rocks.
Now I find out I was using the wrong method to identify gneiss rocks?
Well at least I found out how to identify mean rocks. Does anyone have an aspirin. I have a really bad head ache.
Oh my god