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Cornish Chalcocite but from where?
  
  Index -> What is it? - Where is it from?
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jfc035




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PostPosted: May 28, 2017 06:20    Post subject: Cornish Chalcocite but from where?  

Hello
I've found this week-end in a local show this small chalcocite in an old collection (2.5 cm large). The only information was "Chalcocite - UK"
The crystals are highly lustrous and razor-shaped. They sit on a piece of what I assume to be iron-stained amorphous quartz ; there is a bit of limonitic oxidation on the backside of chalcocite.
Does it ring any bell to Brit colleagues / collectors where it may actually come from?
Thanks
Jean-François



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jfc035




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PostPosted: May 28, 2017 06:23    Post subject: Re: Cornish Chalcocite but from where?  

I forgot to mention that it seems there is a bit a chalcopyrite underneath the chalcocite (see top two pictures)
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Tobi




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PostPosted: May 28, 2017 07:25    Post subject: Re: Cornish Chalcocite but from where?  

I'm neither an expert for chalcocite nor for British minerals, but I know such superb and lustrous crystals of that mineral from Geevor Mine in Cornwall ...
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GneissWare




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PostPosted: May 28, 2017 14:20    Post subject: Re: Cornish Chalcocite but from where?  

There are many Cornwall localities, and likely other UK localities. If you don't get an answer here, there is a very active facebook group, search for "Collectors of British Minerals". Ian Bruce is on that page, and may know.

Great specimen by the way!
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markbeckett




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PostPosted: May 29, 2017 06:01    Post subject: Re: Cornish Chalcocite but from where?  

Hi jfc035 - I agree with Tobi - if this is a UK specimen, it is almost certainly from Geevor Mine, near St Just, Cornwall. Other localities in Cornwall, such as St Ives Consols and Cook's Kitchen at Pool also hosted chalcocite, but I have never seen really lustrous 'razor-like' crystals like yours from anywhere else in UK - other than from Geevor. North Pig Lode and Hanging Wall Vein at Geevor were well-known for producing these excellent crystals - many of these specimens were collected, even in the later years of the old mine (mining in this district has been going on for over 300 years). The quartz matrix with a spot of chalcopyrite is also quite probable (for Geevor).

Thanks for showing this great little piece :-)
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jfc035




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PostPosted: May 29, 2017 14:19    Post subject: Re: Cornish Chalcocite but from where?  

Dear All
thanks for your replies and tips.
Best regards
Jean-François
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