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Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite
  
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tchai




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PostPosted: Dec 03, 2018 20:19    Post subject: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

Hello all,

This was recently given to me as a gift. The locale is unknown. The translucent grey/black crystals form perfect cubes and have a glassy luster. I was told that this was not dyed or enhanced.

My initial guess was that this is a fluorite specimen since the crystals form such distinct cubes, but I've never seen such dark fluorite before - it still looks dark grey/black in the sunlight, unlike other fluorite I have seen which are usually much more opaque and will look purple under light. Any thoughts are appreciated!



black 1.JPG
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black 1.JPG



black 2.JPG
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black 2.JPG


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Tobi




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PostPosted: Dec 04, 2018 02:34    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

Without a doubt this should be fluorite.
tchai wrote:
but i've never seen such dark fluorite before - it still looks dark grey/black in the sunlight, unlike other fluorite i have seen which are usually much more opaque and will look purple under light. any thoughts are appreciated!
Fluorite occurs in nearly ALL colours and from deep black to bright white. And there's also a wide range from opaque to transparent. But the ones you mention that look purple under (sun)light are quite rare, this is a typical phenomenon of some English fluorites.

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Tobi
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SteveB




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PostPosted: Dec 04, 2018 03:05    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

Yep, fluorite. Great gift
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tchai




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PostPosted: Dec 04, 2018 08:44    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

Thank you for your input! You mention English fluorite - do you happen to know of the specific region they are usually found? I'm just beginning to catalog my collection.
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Tobi




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PostPosted: Dec 04, 2018 09:40    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

tchai wrote:
thank you for your input! you mention english fluorite - do you happen to know of the specific region they are usually found? i'm just beginning to catalog my collection.
England is, like Germany, a country with a lot of classic fluorite localities, many of them are in Durham, e.g. Rogerley Mine, Blackdene Mine, Boltsburn Mine, Frazer's Hush Mine, Heights Quarry, West Pasture Mine and many many more, another very famous one is Hilton Mine in Cumbria. I recommend further information to get an overview over the variety of English fluorites, here are some links:

http://www.kureczka-martin.com/MinesIntro.htm
http://www.kureczka-martin.com/History.htm
http://www.kureczka-martin.com/Geology.htm
http://www.kureczka-martin.com/Weardale.htm
http://www.kureczka-martin.com/Rookhope.htm
http://www.kureczka-martin.com/Northumberland.htm
http://www.kureczka-martin.com/Cumbria.htm
http://www.kureczka-martin.com/Yorkshire.htm
(Many many MANY!!! detailed information about fluorite mining in England, including plenty of superb descriptions, photos and maps)

https://issuu.com/irocks/docs/greenbank_book_-_complete_reduced
(An eBook about the famous Greenbank collection, including many information about famous British mining regions)

And concerning those fluorites that show purple/blue daylight fluorescence: I think the most famous ones are those from Rogerley Mine, but I'm sure other collectors have more knowledge than me ...

Regards
Tobi
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tchai




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PostPosted: Dec 04, 2018 09:41    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

Thank you again! This is all very helpful information for someone just beginning to study mineralogy.
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Bob Harman




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PostPosted: Dec 04, 2018 16:35    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

Yours is actually quite a generic specimen. The intergrown fluorite cubes are actually paler in purple color than they look under some lights.

Identical examples come from the mining districts in southern Illinois as well. BOB
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colin robinson




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PostPosted: Dec 04, 2018 18:03    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

As an Englishman and collector of fluorites for 50 years I have to say I've never seen anything quite like that from here. I have seen similar material from the U.S. so I'd say Bob's reply is more likely.
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R Saunders




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PostPosted: Dec 05, 2018 05:33    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

From my wife's mother.
Fluorite and BARITE
Crystal Victory Mine, Cave-in-Rock, Illinois, USA
756 grams



Flourite (2).JPG
 Mineral: Fluorite and Barite
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Flourite (2).JPG


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Tobi




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PostPosted: Dec 05, 2018 10:23    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

R Saunders wrote:
From my wife's mother.
Fluorite and BARITE
Crystal Victory Mine, Cave-in-Rock, Illinois, USA
756 grams
An interesting specimen, but what has it to do with the mineral ID question in this thread?
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Bob Harman




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PostPosted: Dec 05, 2018 10:48    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

As TOBI said, not of meaning in this thread.

This is a piece of massive fluorite and barite (maybe some mixed calcite as well) from the edge of an orebody from the Illinois fluorite district. Classic appearance with no intact crystals of either mineral; just massive.

I might mention that giving the "weight" of these type specimens is really of no importance as it is just a reflection of how "big" your example is. Much more important would be the specimen size, either in inches or centimeters. BOB
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Kevin Conroy




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PostPosted: Dec 05, 2018 15:09    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

tchai, please post a picture of the back of the specimen. Sometimes collectors can recognize where it is from by the matrix.
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tchai




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PostPosted: Dec 05, 2018 16:05    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

Sure. This is back of the matrix. Thank you again for all your help!


36773CEB-1D27-4F14-847A-E04DD01059B9.jpeg
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Fluorite matrix (back)
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36773CEB-1D27-4F14-847A-E04DD01059B9.jpeg


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Kevin Conroy




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PostPosted: Dec 05, 2018 20:03    Post subject: Re: Mineral ID Help: cluster of small translucent black cubic crystals - possibly fluorite  

Thank you for the matrix photo. This doesn't look familiar to me, but maybe someone else will recognize it.
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