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Black stones
  
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Marjolein van Braak




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PostPosted: Aug 28, 2021 06:35    Post subject: Black stones  

I am not really sure about those 2 stones. My 2 guesses are black hornblende or black tourmaline, but it could be that I am wrong, black stones drive me crazy at times. I also have no clue where those two pieces come from. In the bigger piece you can sometimes see an orange (and a little rainbow) shimmer.

P.S. I just have a box with around 50 pieces of crystals and rocks that I don't know names or locations of. So.. be prepared there will follow some more posts.



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James Catmur
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PostPosted: Aug 28, 2021 06:45    Post subject: Re: Black stones  

We are very happy to help, but could you please do a few tests before each post as that helps more than photos

Tests 7 and 8 would really help you.

I suspect you will find the hardness of the 2nd specimen is 7 to 8, and if it is you may well be looking at Black Tourmaline ('Schorl'). Hornblende is softer (5 to 6). Does it scratch quartz (i.e. it is harder) or is it scratched by quartz (i.e. it is softer).

The streak will not help you as much as the hardness with these two minerals

https://www.mineral-forum.com/message-board/viewtopic.php?p=19487#19487
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Marjolein van Braak




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PostPosted: Aug 28, 2021 07:14    Post subject: Re: Black stones  

Thank you for the reply, the hardness of the second specimen is indeed about the same as quartz. The second one is a little bit harder to determine, but I think it is also approximately the same. Quartz is maybe a little bit harder. So that would conclude that those both are tourmaline or schorl as you stated.

Is there maybe another mineral that it could be, that I overlooked?
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James Catmur
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PostPosted: Aug 28, 2021 09:21    Post subject: Re: Black stones  

If the second one in harder than quartz, then tourmaline is likely. For the first, which is less hard than quartz, it is unlikely.

Check their streaks as that may help a bit
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John Betts




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PostPosted: Aug 28, 2021 10:07    Post subject: Re: Black stones  

They are most likely black tourmaline. Probably schorl.
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