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413 Views 3 Replies Last post: May 19, 2013 11:12 PM by MikeHardman RSS
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May 16, 2013 10:39 AM

Dinosaur egg?

Just kidding, I know it's not a dinosaur egg!

But I would love to know what it's made of?

I found this beautiful rock by a glacial meltwater river in the Pindari valley in the Indian Himalayas. It's got lots of stripes and different colours, and silver shiny flecks all over.

Thank you.

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    May 16, 2013 11:16 AM (in response to Yasmin)
    Re: Dinosaur egg?

    Yasmin,

     

    [smiley]

     

    The sparlkly bits are mica, probably both white mica (muscovite) and dark mica (biotite). The paler minerals forming the majority of the rock are probably feldspar and quartz (difficult to be sure without microscope examination). Since there is no sign of pink feldspar, it is probably of intemediate acidity. Therefore, in terms of mineral assemblage, it is probably at the diorite end of the diorite-granite continuum. However, there is a degree of foliation/banding. Some of that could be primary (in the magma chamber), but it could also be due to a degree of metamorphism, in which case one might call it a metadiorite. To know more about the metaphorphic aspect, one would have to look for other minerals, such as pyroxene / hornblende / garnet.

     

    I bet your rock looked better when it was wet.

    You can keep in in a fountain outside (I know, no everybody has a fountain!).

    But you could also varnish it (perhaps try it on a relatively rubbish rock first, in case you don't like the effect).

     

    Mike

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      • Currently Being Moderated
        May 19, 2013 11:12 PM (in response to Yasmin)
        Re: Dinosaur egg?

        Glad to be of help, Yasmin.

         

        Rocks always have a story to tell. The trick is to know how to read them. But first you have to look. Sometimes you'll find a single rock has little to say; then you may need to find some others nearby - which may be more talkative. Even then, the story may be vague. The outcrop may add some vital context. And the panorama may tell you if the story is a thriller, comedy or perhaps science fiction!  Aha! Now you understand; you've got the lingo. Perhaps close scrutiny of some individual minerals will reveal the sub-plot.

         

        Mike

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