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Green crystals in Pegmatite?
  
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fuss




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PostPosted: Oct 19, 2018 22:54    Post subject: Green crystals in Pegmatite?  

There are a few patches of these green/turquoise colored crystals on what I think is a Pegmatite. I'm not sure how to test them since they are so embedded, any ideas on what they might be? I pulled this rock out of lake Michigan's surf in Wisconsin.

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pegmatite.jpg



green mineral.jpg
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green mineral.jpg



pegmatite4.jpg
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pegmatite4.jpg


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Josele




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PostPosted: Oct 20, 2018 06:28    Post subject: Re: green crystals in Pegmatite?  

Hard to say without seeing any crystal face but in a pegmatite and with this color I think it could be tourmaline. Try to check the hardness...
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crosstimber
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PostPosted: Oct 20, 2018 09:32    Post subject: Re: Green crystals in Pegmatite?  

As Josele suggested, it could be tourmaline. Another possibility is apatite. these should be easy to distinguish by checking hardness. Apatite is 5 and tourmaline is 7 to 7.5. Try scratching with a steel knife (about 5). If it does not scratch, try a piece of quartz = 7. That will eliminate some possibilities. The colorless to white mineral it is embedded in is quartz.
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kushmeja




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PostPosted: Oct 20, 2018 12:18    Post subject: Re: Green crystals in Pegmatite?  

It looks very similar, especially with respect to the color, to apatite that I've seen from southeastern PA. As suggested, hardness test would be a good indicator.
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vic rzonca




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PostPosted: Oct 20, 2018 15:13    Post subject: Re: Green crystals in Pegmatite?  

One other possibility is beryl. Just from the image, I vote for apatite.
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fuss




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PostPosted: Oct 21, 2018 10:50    Post subject: Re: Green crystals in Pegmatite?  

There does not seem to be enough of it exposed to scratch properly, it just basically crushed it into sand sized grains when I tried.
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Bob Carnein




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PostPosted: Oct 21, 2018 10:56    Post subject: Re: Green crystals in Pegmatite?  

If the mineral crushes, try scraping the grains between two flat pieces of glass. If it is tourmaline, it will scratch the glass easily.
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vic rzonca




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PostPosted: Oct 21, 2018 11:26    Post subject: Re: Green crystals in Pegmatite?  

I also wonder what the black/brown spots are, at 2 and 6 o'clock, in the first image. Microlite?
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fuss




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PostPosted: Oct 21, 2018 12:12    Post subject: Re: Green crystals in Pegmatite?  

I'm not sure what it is, here are a few more images. Just noticed more of the greenish material just below the surface when editing the first shot.


pegmatite minerals.jpg
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pegmatite minerals.jpg



mineral2a.jpg
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mineral2a.jpg



mineral2.jpg
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mineral2.jpg


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fuss




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PostPosted: Oct 21, 2018 22:58    Post subject: Re: Green crystals in Pegmatite?  

ok Ill try that Bob.
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Duncan Miller




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PostPosted: Oct 22, 2018 01:31    Post subject: Re: Green crystals in Pegmatite?  

Looking at your photos of 21 October, the black mineral looks like tourmaline and the greenish blue mineral like apatite. Try the crushing test between glass for each of these separately.
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Pete Modreski
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PostPosted: Oct 22, 2018 11:33    Post subject: Re: Green crystals in Pegmatite?  

My first thought was also apatite. Beryl is usually not this dark a blue color. Tourmaline is also a good candidate too, but, since the black mineral with it is almost certainly black tourmaline (schorl) but, if one type of tourmaline is present, one would not expect a second type of tourmaline to also be present nearby in the same rock in separate crystals. So I think our consensus is, pretty sure this is apatite.
Another test, if you have access to a short-wave UV light, some (but not all, so this isn't positive) apatite from pegmatites fluoresces yellow-orange under shortwave UV; tourmaline, almost never. But it's the dark blue apatite that is least likely to show the fluorescence so as I say, this might provide a confirmation, but a lack of response would not warrant a negative conclusion.
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fuss




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PostPosted: Oct 22, 2018 18:05    Post subject: Re: Green crystals in Pegmatite?  

Thx Pete, I have a long wave uv but not a short wave light... but I have always wanted to get one so now I just may do that. It showed nothing really under the long wave though.


Pete Modreski wrote:
My first thought was also apatite. Beryl is usually not this dark a blue color. Tourmaline is also a good candidate too, but, since the black mineral with it is almost certainly black tourmaline (schorl) but, if one type of tourmaline is present, one would not expect a second type of tourmaline to also be present nearby in the same rock in separate crystals. So I think our consensus is, pretty sure this is apatite.
Another test, if you have access to a short-wave UV light, some (but not all, so this isn't positive) apatite from pegmatites fluoresces yellow-orange under shortwave UV; tourmaline, almost never. But it's the dark blue apatite that is least likely to show the fluorescence so as I say, this might provide a confirmation, but a lack of response would not warrant a negative conclusion.
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fuss




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PostPosted: Oct 22, 2018 18:09    Post subject: Re: Green crystals in Pegmatite?  

If I can get some of this out I will do just that, I am having a bit of an issue getting any of it out though..

Duncan Miller wrote:
Looking at your photos of 21 October, the black mineral looks like tourmaline and the greenish blue mineral like apatite. Try the crushing test between glass for each of these separately.
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