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20 Jul-21:47:30 Re: sainte marie-aux-mines show 2018 (Roger Warin)
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20 Jul-16:14:13 Re: glass or something else? (Vic Rzonca)
20 Jul-14:12:47 The mizunaka collection - orthoclase (Am Mizunaka)
20 Jul-13:25:34 Re: all the diamonds one could fill your house with - and more - so near...yet so far..... (Peter Lemkin)
20 Jul-11:59:54 Re: glass or something else? (Justin Hickok)
20 Jul-11:09:23 Re: all the diamonds one could fill your house with - and more - so near...yet so far..... (Justin Hickok)
20 Jul-11:08:35 Re: all the diamonds one could fill your house with - and more - so near...yet so far..... (Justin Hickok)
20 Jul-00:28:07 Re: sainte marie-aux-mines show 2018 (Roger Warin)
20 Jul-00:20:30 Re: sainte marie-aux-mines show 2018 (Roger Warin)
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19 Jul-15:40:28 Re: sainte marie-aux-mines show 2018 (Roger Warin)
18 Jul-16:00:11 The mizunaka collection - quartz (Am Mizunaka)

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Agate?
  
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DianaClaraB




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PostPosted: Apr 10, 2018 12:37    Post subject: Agate?  

Hello everybody,

I am asking for your help.I found this rock which looks like an agate, but I'm not sure if it is one or which kind of agate it is. I am really interested in finding out what kind of rock is this and I would be really thankful if anybody could help me.
Thank you very much.



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James
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PostPosted: Apr 10, 2018 13:06    Post subject: Re: Agate?  

Please tell us where it is from and do some of the basic tests (hardness, streak) discussed on this page

http://www.mineral-forum.com/message-board/viewtopic.php?p=19487#19487

Without that my best guess is 'a pebble'

James
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Bob Harman




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PostPosted: Apr 10, 2018 13:15    Post subject: Re: Agate?  

Agate is usually defined as cryptocrystalline quartz with a noticeable banding pattern.
While your specimen might be a broken piece of a former agate, it does not now show any banding patterns so it is now probably a simple piece of chalcedony.
For a learning experience, you can do all the testing you want, but on a piece like yours, it probably is just not worth the time. BOB
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John Betts




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PostPosted: Apr 10, 2018 13:51    Post subject: Re: Agate?  

Check hardness. It looks like it might be calcite.

Try scratching glass. Agate (quartz) will scratch it, calcite will not.

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Bob Harman




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PostPosted: Apr 10, 2018 14:12    Post subject: Re: Agate?  

JOHN, On the poster's photo there appears to be some CHONCHOIDAL fracturing.This is typical for most types of quartz. Calcite CLEAVES and, to my eye, there is NO cleaving in the photo. However, it seems appropriate, if you want, to test with a bit of vinegar. Fizzing = calcite; no fizzing = not calcite.
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DianaClaraB




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PostPosted: Apr 10, 2018 14:45    Post subject: Re: Agate?  

I found it in a hilly village in Central Transylvania, Romania. I checked the hardness and it scratches glass. Thank you for your response.
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Kevin Schofield




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PostPosted: Apr 10, 2018 15:07    Post subject: Re: Agate?  

It is certainly a piece of chalcedony (the very finely crystalline quartz that makes up agates). The characteristic that would make it an agate is (as somebody else on this thread said) some sort of banded composition. On the "thin" edge that is just visible in your photograph, it looks as if there may be some subtle pink/white bands? If so, then you might call this an agate. If not, you can just call it a piece of pink chalcedony.

You'll find everything you would probably want to know about agate here:

https://en.wikipedia.org/wiki/Agate

Happy hunting if you go looking for more :-)

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alanbartlett




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PostPosted: Apr 11, 2018 09:17    Post subject: Re: Agate?  

As an enthusiastic, though infrequent!, collector and processor of agates from Scotlands beaches may I suggest that the external texture would suggest that it is an agate - i.e. very uneven with pot-marks. As Kevin suggested there does seem to be a hint of waviness on the bottom edge - would it be possible to get a clearer image of this bottom edge?
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