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Thread: Please help me identifying these rocks

  1. #1 Please help me identifying these rocks 
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    Hello all,

    For some reason I can't attach a photo on here so I'll try inserting a link of the photo I uploaded on my fb wall.

    https://fbcdn-sphotos-c-a.akamaihd.n...06853636_o.jpg

    Identifying these rocks would be important to me hence I use these in the potting mixes I make for my cacti. Someone told me they are dacite- I have a feeling they're more likely related to granite .

    All the best,
    Laszlo


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  3. #2  
    Forum Professor scoobydoo1's Avatar
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    My first two guess are Granodiorite and Diorite, and they do share similarities with Granite (although I do not think your specimens are granite judging from your photograph).


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  4. #3  
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    Thank you scooby!
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  5. #4  
    Universal Mind John Galt's Avatar
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    I hesitate to make any identification based upon such badly weathered samples. Certainly they are plutonic igneous rocks, so that rules out dacite.

    I lack scooby's confidence in distinguishing between granodiorite and granite on such weathered specimens. Although I am marginally more comfortable with the call on diorite.
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  6. #5  
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    Quote Originally Posted by John Galt View Post
    I lack scooby's confidence in distinguishing between granodiorite and granite on such weathered specimens. Although I am marginally more comfortable with the call on diorite.
    I wouldn't call it confidence, but based on the descriptions found in my copy of Handbook for Rocks And Minerals, they appear to be the best fit when compared with the image Laszlo76 has provided. I did say they were guesses after all.





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  7. #6  
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    Thank you very much for the comments- based on the photos and descriptions provided by scooby I would bet on granodiorite...

    Either way, 75% of the potting mix that I make for my cacti consists of this rock- and my plants seem to love it even if I don't add anything organic to the mix at all.

    https://www.facebook.com/laszlo.ambr...6057214&type=3

    Have a great week.
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  8. #7  
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    There's an other rock I'm puzzled about- is it scoria?

    https://fbcdn-sphotos-b-a.akamaihd.n...35725375_o.jpg

    And here's the place that's littered with it:

    https://fbcdn-sphotos-g-a.akamaihd.n...05344968_o.jpg

    Regards,
    Laszlo
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  9. #8  
    Forum Professor scoobydoo1's Avatar
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    Quote Originally Posted by Laszlo76 View Post
    There's an other rock I'm puzzled about- is it scoria?

    https://fbcdn-sphotos-b-a.akamaihd.n...35725375_o.jpg
    I can't really make out what those are from the image and there isn't a suitable match in my guidebook, but some of them do appear to have bubble-like cavities. Would you happen to have a closeup shot of one of them?

    Quote Originally Posted by Laszlo76 View Post
    And here's the place that's littered with it:

    https://fbcdn-sphotos-g-a.akamaihd.n...05344968_o.jpg
    Those two rocks resemble banded ironstone from my guidebook. Perhaps someone else can identify what they are.

    Nice scenery by the way. I'd always wished that Singapore had landscapes like that where I could go "investigate". Even as a child, I'd always fantasied about wandering around places like that; with a novice pickaxe and picking out samples. Sigh.
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  10. #9  
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    https://fbcdn-sphotos-g-a.akamaihd.n...65465929_o.jpg

    There it is, Scooby- the photo was taken in the morning, it didn't turn out too well.

    I've been to quite a few places like this, studying birds and plants- wish I payed more attention to petrology as well...
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  11. #10  
    Forum Professor scoobydoo1's Avatar
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    Quote Originally Posted by Laszlo76 View Post
    https://fbcdn-sphotos-g-a.akamaihd.n...65465929_o.jpg

    There it is, Scooby- the photo was taken in the morning, it didn't turn out too well.
    Comparing this image and the one with a wider angle, it does seem to resemble scoria. This link has some images of basalt scoria samples of different varieties, and it mentions that the brownish/reddish hue may be a result of oxidization of iron minerals.

    Quote Originally Posted by Laszlo76 View Post
    I've been to quite a few places like this, studying birds and plants- wish I payed more attention to petrology as well...
    It's never too late to learn more about the planet we live on. You are a lucky one to have access to such lovely sites. I envy you.


    Edits: Here is the Banded Ironstone entry from my guidebook if you're interested. One thing that caught my eye is that if this is a match to those two big rocks from your photo, you may be able to reach out and touch something formed two to three thousand million years ago!

    Last edited by scoobydoo1; July 20th, 2013 at 07:21 AM.
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