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Thread: What is this rock?

  1. #1 What is this rock? 
    Forum Freshman Deno's Avatar
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    Sorry if this is in the wrong place, just wondering what the purple squares (crystals?) in this rock are...

    IMG_1122[1].jpgIMG_1120[2].jpg


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  3. #2  
    Universal Mind John Galt's Avatar
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    It is quite a heavily weathered sample, which causes me some reservation, but they look like orthoclase, a potassium feldspar, commonplace in acidic igneous rocks.


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  4. #3  
    Forum Freshman Deno's Avatar
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    Cool thanks. Anyone else have any ideas on what it might be? or do you agree with that?
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  5. #4  
    Forum Professor Zwolver's Avatar
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    Does look like heavy volcanic rock, with marble inside.. Not sure about the name.. haha.. i'm no geology expert..
    Growing up, i marveled at star-trek's science, and ignored the perfect society. Now, i try to ignore their science, and marvel at the society.

    Imagine, being able to create matter out of thin air, and not coming up with using drones for boarding hostile ships. Or using drones to defend your own ship. Heck, using drones to block energy attacks, counterattack or for surveillance. Unless, of course, they are nano-machines in your blood, which is a billion times more complex..
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  6. #5  
    Universal Mind John Galt's Avatar
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    Zwolver,
    1. "heavy" is not a standard (or even non-standard) qualifier for igneous rocks.
    2. Volcanic rocks can be porphyritic, with some crystals being of very large size, but they are normally fine grained, baecause of rapid surface cooling. This may just be in this category.
    3. They do not contain "marble inside", whatever that is meant to mean.
    4. Marble, in geology, is a very specific rock type - a thermally metamorphosed limestone. This is not, nor is any part of it, marble.
    5. Making an identification from a photograph of the weathered surface of a rock sample is difficult enough for a bona-fide geologist. Please try not to confuse the issue.


    Deno, I see no quartz grains in the sample, so I rule out the acidic igneous rocks I hinted at in my earlier post. The groundmass has a greenish tinge and I suspect serpentinisation, the chemical weathering of ferromagnesian minerals. Give the absence of quartz, but the abundant orthoclase (cerainly feldspar) porphyroblasts, then I suspect the original ferromagnesian may have been a pyroxene. Given that there are arguably two shades of green there may have been two different pryroxenes present. Put all that together and I would tentaively say you have a trachyte, an intermediate lava.

    Where did you find it? That could help me pin it down further.
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  7. #6  
    Forum Freshman Deno's Avatar
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    I found it in Prince Albert, Saskatchewan, In Canada. Here is another one like it...
    IMG_1171[1].jpgIMG_1172[1].jpg
    The light cubes are somewhat 'shiny'/reflective unlike the darker material surrounding them in both rocks. The first rock I posted (Larger rock) has darker purple squares which blend in slightly more with the surrounding material, but the pieces in this one (smaller rock) are much lighter in colour and only have a tiny tinge of purple, barely purple at all actually. This smaller rock is also slightly more green than the larger rock in regards to the surrounding material.

    I have a lot of rocks I would like looked at, and one I even named Dark Matter, my brother said it reminded him of a symbiote, like carnage from spiderman. I've never seen a rock like it before, was thinking maybe some liquid from a car spilt on it, but then why is it so sparse, shouldn't it be covered. There's a lot of factors I suppose, anyway here it is.
    IMG_1178[1].jpg
    It is a pale red, with Black glossy chunks, especially apparent on the edges of the rock. I may be wrong, but it feels lighter then it should be.
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  8. #7  
    Forum Professor Zwolver's Avatar
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    Quote Originally Posted by John Galt View Post
    Zwolver,
    1. "heavy" is not a standard (or even non-standard) qualifier for igneous rocks.
    Nope, heavy is a measurement of weight, and from the 2 types of volcanic rock i know, one being the foam/pumestone and the otherone being solid, and thus heavy.

    Quote Originally Posted by John Galt View Post
    2. Volcanic rocks can be porphyritic, with some crystals being of very large size, but they are normally fine grained, baecause of rapid surface cooling. This may just be in this category.
    This doesn't look like crystals, it looks like rubble from an explosion to me.

    Quote Originally Posted by John Galt View Post
    3. They do not contain "marble inside", whatever that is meant to mean.
    I meant, apart from the pink, it looked like smooth broken rubble, that was caught in a lava stream. The only light colored rock i could think of at the moment was marble.

    Quote Originally Posted by John Galt View Post
    4. Marble, in geology, is a very specific rock type - a thermally metamorphosed limestone. This is not, nor is any part of it, marble.
    I know, it probably isn't but at 5 you stated that you can't rule it out, as it is difficult to see.

    Quote Originally Posted by John Galt View Post
    5. Making an identification from a photograph of the weathered surface of a rock sample is difficult enough for a bona-fide geologist. Please try not to confuse the issue.
    Of that i know, but the mineral was questioned out of curiosity, i answer without full knowledge, and reporting i didn't know. So what did i do wrong?
    Growing up, i marveled at star-trek's science, and ignored the perfect society. Now, i try to ignore their science, and marvel at the society.

    Imagine, being able to create matter out of thin air, and not coming up with using drones for boarding hostile ships. Or using drones to defend your own ship. Heck, using drones to block energy attacks, counterattack or for surveillance. Unless, of course, they are nano-machines in your blood, which is a billion times more complex..
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  9. #8  
    Forum Professor Zwolver's Avatar
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    Quote Originally Posted by Deno View Post
    It is a pale red, with Black glossy chunks, especially apparent on the edges of the rock. I may be wrong, but it feels lighter then it should be.
    This makes me think of obsidian with an ferrous coating, but galt will say i'm wrong any minut now, so whatever..
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    Growing up, i marveled at star-trek's science, and ignored the perfect society. Now, i try to ignore their science, and marvel at the society.

    Imagine, being able to create matter out of thin air, and not coming up with using drones for boarding hostile ships. Or using drones to defend your own ship. Heck, using drones to block energy attacks, counterattack or for surveillance. Unless, of course, they are nano-machines in your blood, which is a billion times more complex..
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  10. #9  
    Forum Radioactive Isotope Paleoichneum's Avatar
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    Zwolver- When it comes to "heavy" as a descriptive term, it is very very hard to use in geology. The overall perceived weight of a specimen will be entirely dependent on what minerals are in its composition. If it is full of copper sulfides from Butte Monatana its going to be much heavier then if its material generated during the 1980 Mt St Helens eruptions.
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  11. #10  
    Forum Freshman Deno's Avatar
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    If weight will help you identify these items, them I will put the weights and dimensions. Give me a bit to find my scale =]
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  12. #11  
    Forum Radioactive Isotope Paleoichneum's Avatar
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    Sadly it will not help with the identification. But on the other hand Im in agreement with John that its feldspar crystals in metamorphics. If you want more specifics you could try the identification forum at Mindat.org
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  13. #12  
    Forum Freshman Deno's Avatar
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    Thanks for the link.
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  14. #13  
    Universal Mind John Galt's Avatar
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    Paleoichnium, I didn't say metamorphics, but a porphyritic intermediate lava. I don't see it likely one could grow feldspars that size and maintain the ground mass crystals an order of magnitude or more smaller. It couldn't happen in a regional stress environment - which is clearly not present due to non-alignment of the crystals. While I concede an outside possibility of growth in a thermal aureole, I would have expected less elongate growth - rather more equidimensional crystals. That would certainly match the crystal form of orthoclase I've seen in thermal metamorphism.

    Zwolver, what you 'have done wrong' is to speak confidently, but make many incorrect or misleading statements. If you sounded like you were talking crap it wouldn't be a problem. (By the way, from me, that counts as a compliment.)

    Deno,
    part of the difficulty is that a geologist would almost immediately break the samples in two, to have a fresh surface to examine. I'm not urging you to do this by the way. Keep it whole.

    The second rock you showed, the red/pink one: my first reaction was . But almost immediately it occured to me it may be a chert nodule with a sedimentary coating rich in iron oxide. That is a gues. Are the black portions shiny and hard, with no visible crystals?

    I'm still readin up on the geology of the region to see if that clarifies anything. I am interested to learn that Saskatchewan has six meteor craters - astroblemes - that have impacted (pun intended) the geology of the area. I don't think your samples are associated with these, however.
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  15. #14  
    Forum Radioactive Isotope Paleoichneum's Avatar
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    Thanks for the correction John!
    If more of us valued food and cheer and song above hoarded gold, it would be a merrier world. -Thorin Oakenshield

    The needs of the many outweigh the need of the few - Spock of Vulcan & Sentinel Prime of Cybertron ---proof that "the needs" are in the eye of the beholder.
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  16. #15  
    Forum Professor Zwolver's Avatar
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    Quote Originally Posted by John Galt View Post
    Zwolver, what you 'have done wrong' is to speak confidently, but make many incorrect or misleading statements. If you sounded like you were talking crap it wouldn't be a problem. (By the way, from me, that counts as a compliment.)
    I still don't get it, how is this, speaking confidently???

    Does look like heavy volcanic rock, with marble inside.. Not sure about the name.. haha.. i'm no geology expert..
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    Growing up, i marveled at star-trek's science, and ignored the perfect society. Now, i try to ignore their science, and marvel at the society.

    Imagine, being able to create matter out of thin air, and not coming up with using drones for boarding hostile ships. Or using drones to defend your own ship. Heck, using drones to block energy attacks, counterattack or for surveillance. Unless, of course, they are nano-machines in your blood, which is a billion times more complex..
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  17. #16  
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    Zwolver, I think the point is that another person reading that might think your comment had some scientific weight--that you know something they don't know, regardless if you are an expert or not. For example, I might look at something and think "it looks like marble" and then go to a science forum and someone else says "it looks like marble". At that point I'm feeling pretty sure it is marble--even though I have no idea what that means (how is marble defined/classified scientifically). I guess you could say it is up to the reader to be aware that not all comments are scientifically grounded, but I know from experience it is not always clear who is speaking from authority and who is casually speculating. If you want to ensure no confusion, you'd have to either remain silent on the topic OR include a stronger disclaimer: "So, this is completely uninformed speculation here, since I know nothing about geology, but it sure looks like chunks of marble stuck in a volcanic rock." Anyway, that's my approach. Might not work for everybody.
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  18. #17  
    Universal Mind John Galt's Avatar
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    Zwolver, exactly what Joshuat said. Thank youfor saving me the effort Joshuat.
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  19. #18  
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    it looks like a weathered breccia with pieces taken from a rock that had some sort of igneous matrix.

    You should try looking for grains within the rock. Does it appear to be sedimentary? Are the grains mafic or felsic looking?
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