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Help identifying my stone. UK coastline.
  
  Index -> FOR BEGINNERS: What is it? Where is it from?
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iceantia




Joined: 02 Nov 2017
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Location: Worcester

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PostPosted: Nov 03, 2017 00:58    Post subject: Help identifying my stone. UK coastline.  

Hello all. Hopefully I am in the right place and someone can help me?
I have had this stone since I was little and I have kept it all this time.
I would love to know what it is!
The rock itself was found on the UK coastline. I can't remember exactly where but would imagine South Wales or Cornwall as that was where we often went.
It is a dark green nearly black colour with patches of orange and a orange colored vein. It is completely smooth to touch and is always cold. It is fairy heavy. Hopefully that is all the info you need?
Thank you :)



20171102_232009.jpg
 Mineral: Unknown
 Dimensions: 8cm x 6cm
 Description:
 Viewed:  338 Time(s)

20171102_232009.jpg


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Jordi Fabre
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PostPosted: Nov 03, 2017 02:35    Post subject: Re: Help identifying my stone. UK coastline.  

We understand your desire to know what your samples are, but it is too difficult to determine this from photos. If you have a rock shop nearby, or a lapidary club, we would suggest you go there to ask. In case for some reason you can't join a club then you can also try this other web page: https://www.reddit.com/r/whatsthisrock . You can also read Asking: What is it? - Where is it from? and provide us with some basic information about the specimen.

We want to help those who are truly curious, but you need to give us more information before we can help you. Sorry to be so strict but we receive too many queries from people asking more or less similar questions and finally we have been a little bit saturated by those kind of requests without no more information than the images.

Thanks for understanding
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Pete Modreski
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PostPosted: Nov 03, 2017 11:59    Post subject: Re: Help identifying my stone. UK coastline.  

Dear Iceantia,
I'm sure you will understand, as per Jordi's reply, that first there are just not any very distinctive features about this pebble that would help us to even make a good guess as to its identity, and second, that our Forum is really more aimed at experienced mineral collectors sharing information about interesting and unusual crystallized mineral specimens.

That being said, let me just share a word or two of advice anyway. If you read about rocks and minerals, you'll find that there are a number of kinds of rocks that can match the appearance of your pebble--very fine-grained, mottled darkish colors, no obvious layering and no obvious crystals present, and the thin white band which might be a vein of quartz or calcite. There are just too many kinds of fine-grained rocks like this--and it could be either sedimentary, or metamorphic (most likely only slightly metamorphosed, since there are no obvious crystals that have formed in it), or even igneous (though your rock does not show any obvious igneous features). As you'll learn, two very simple tests you can do on the rock, that will help you narrow things down, would be: can you scratch it with a knife? If you can't--if a knife point only leaves a streak of metal on the surface--it could be some form of fine-grained quartz, like jasper. And the second test, obtain some dilute hydrochloric acid, and see if the stone (or the white streak in it) bubbles when a drop of acid is put on it; if so, it is made of limestone (the rock) or calcite (the mineral vein). These, of course, should also be soft and easily scratched.
Let me just add some of the types of rock that your stone COULD be, just to guide you. And one thing to keep in mind, even though books describe rocks as if they were always clear-cut, distinctly different types, is that in nature all types of rock can be gradational between one another, as for example a silty limestone or a limey siltstone. I'll list some of what I might guess are the most likely kinds of rock that your stone might be, starting with the most likely:
Siltstone; meta-siltstone; argillite; slate, jasper; quartzite; limestone; dolomite
And remember what I said, about the rock types being gradational; to invent an extreme example, one could have a slightly metamorphosed, argillaceous dolomite, partly silicified into jasper! (But, really, this is so.)
As a parting comment, I would like to mention a book that you might enjoy reading. It is one that I read and appreciated, as a geologist, but it is written for the lay person, and it explains a great deal about geology and the history of the Earth, as seen through the examination of a single pebble. The book is: "The Planet in a Pebble: A Journey Into Earth's Deep History", by Jan Zalasiewicz. And the pebble that the author uses as his example of what kind of history a single rock can have, is, very appropriately for you, a beach pebble from Wales, which in fact does not look extremely different than your own rock, as you'll see if you look up this book online.
Best of luck getting some insight into this, Pete Modreski
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