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eutaxitic




Joined: 05 Aug 2017
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PostPosted: Aug 05, 2017 09:15    Post subject: What is this?  

I think It must be polymorph of quartz. What do you think?


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Bob Carnein




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PostPosted: Aug 05, 2017 09:20    Post subject: Re: What is this?  

Offhand, it looks like chalcedony. Check to see whether it scratches glass.
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Bob Harman




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PostPosted: Aug 05, 2017 10:07    Post subject: Re: What is this?  

What ever it is, it is seriously iron stained. You can plainly see the rusty iron staining leaching out from the seam into the surrounding matrix. It would have been easier to id the seam had it not been secondarily iron stained. A quartz seam with lots of tarnished and corroding pyrite in it???

Anyway, where was it found? What is the surrounding matrix rock.....sedimentary, igneous, or metamorphic etc? All that info is useful in this case. And, by the way, what ever it will be, it would not be (in my opinion) a "polymorph" of quartz. While there are polymorphs of quartz (they are alpha and beta quartz) with several different mineral names, your pix most probably is not one of them. BOB
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vic rzonca




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PostPosted: Aug 05, 2017 10:44    Post subject: Re: What is this?  

Polymophs of Quartz

Cristobalite
Tridymite
Quartz (high)
Quartz (low)
Coesite
Stishovite

I think you have a cryptocrystalline form of quartz.

Chalcedony
Agate
Carnelian
Chrysoprase
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eutaxitic




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PostPosted: Aug 07, 2017 12:51    Post subject: Re: What is this?  

Its a cryptocristalline quartz, a chalcedony with Botryoidal habitus, Here there is another photo. Occurence is a Secondary infilling of quartz, as geod structure on the volcanic rock.


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