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Questions about a garnet
  
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Richard Arseneau




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PostPosted: Apr 11, 2019 12:48    Post subject: Questions about a garnet  

Hello everyone, I purchased a specimen labeled "manganese Spessartine aluminum garnet" from Tongbei, Yunxiao, Zhangzhou Prefecture, Fujian Province, China.

My first question is what is the proper way to refer to this specimen. Would it be Spessartine (Garnet Group)?

The second question is regarding a small amount of a second mineral on the specimen that appears to have formed after the garnet. I am unable to perform many tests on such a small secondary mineral, but I can tell you it is not attracted to a magnet and Fluorite will not scratch the largest black portion on the back. I am hoping someone familiar with the locality can give me an answer from a few photographs.

Thanks,
Richard



sa.jpg
 Mineral: Garnet Group
 Locality:
Tongbei, Yunxiao, Zhangzhou Prefecture, Fujian Province, China
 Dimensions: 4 X 2.5 cm
 Description:
 Viewed:  766 Time(s)

sa.jpg



sc.jpg
 Mineral: Garnet Group
 Locality:
Tongbei, Yunxiao, Zhangzhou Prefecture, Fujian Province, China
 Dimensions: FOV 1 cm
 Description:
 Viewed:  762 Time(s)

sc.jpg



sb.jpg
 Mineral: Garnet Group
 Locality:
Tongbei, Yunxiao, Zhangzhou Prefecture, Fujian Province, China
 Dimensions: 4 X 2.5 cm
 Description:
Back of the specimen. Not much of a matrix.
 Viewed:  773 Time(s)

sb.jpg


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Tobi




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PostPosted: Apr 11, 2019 13:35    Post subject: Re: Questions about a garnet  

Richard Arseneau wrote:
My first question is what is the proper way to refer to this specimen. Would it be Spessartine (Garnet Group)?
I think this would be a proper way. Or just "Spessartine" :-)
Richard Arseneau wrote:
The second question is regarding a small amount of a second mineral on the specimen that appears to have formed after the garnet. I am unable to perform many tests on such a small secondary mineral, but I can tell you it is not attracted to a magnet and Fluorite will not scratch the largest black portion on the back. I am hoping someone familiar with the locality can give me an answer from a few photographs.
I don't know, but I would guess it is some kind of iron oxide or manganese oxide ...
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Kevin Conroy




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PostPosted: Apr 11, 2019 14:38    Post subject: Re: Questions about a garnet  

I think Tobi nailed it with "spessartine", and some sort of iron or manganese oxide on the back. The black on the front could also be this, or perhaps hematite.
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Ed Huskinson




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PostPosted: Apr 11, 2019 15:26    Post subject: Re: Questions about a garnet  

Wow Richard, what a pretty garnet group!! I'm envious. Enjoy your specimen.

Ed in Kingman

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Jordi Fabre
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PostPosted: Apr 11, 2019 16:47    Post subject: Re: Questions about a garnet  

The Garnets from Tongbei are Spessartines (analyzed).
The black materials are manganese oxides (analyzed)
The brown corroded crystals on the back side of the specimen could be Helvine. We analyzed some from this deposit and them looks like these corroded ones.
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Richard Arseneau




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PostPosted: Apr 11, 2019 16:57    Post subject: Re: Questions about a garnet  

Thank you for the responses eveyone! Ed, even though it is on the small side I do really like this specimen. The colour is very intense. Jordi, it is very nice to get a definitive answer on the manganese oxides.

You guys are great,
Richard
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Tobi




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PostPosted: Apr 12, 2019 10:29    Post subject: Re: Questions about a garnet  

Richard Arseneau wrote:
You guys are great
The FMF Mineral Task Force - always at your service!
;-)
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