July 11-12:BILLINGS, MONTANA: Annual show; Billings Gem and Mineral Club; Sat. 10-5, Sun. 10-4; Free admission!
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 Post subject: paperweight and potato
PostPosted: Fri Jun 05, 2020 5:08 am 
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147 grams corundum and 39 grams grossular. I found both in the alluvial environment of the former largest primary corundum deposit in the Umba Valley. Locals call the paperweight "Ruby Nut".


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 Post subject: Re: paperweight and potato
PostPosted: Fri Jun 05, 2020 4:55 pm 
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Impressive!
Any chance of faceting that grossular, or is it cab grade? Looks like it has a stunning gem inside it either way.

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 Post subject: Re: paperweight and potato
PostPosted: Sat Jun 06, 2020 10:22 am 
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I would love to have a look inside that grossular garnet.

Primary deposit in the oval serpentines structure shown here?


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 Post subject: Re: paperweight and potato
PostPosted: Sat Jun 06, 2020 10:35 am 
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As far as I know, these crystals usually have visible inclusions. So does this one. Wouldn't stand in the way of further processing, though.

I've had my hands on about a dozen of these rough stones. What they all had in common were white, needle-pointed inclusions, visible with a 10x magnifying glass, which are running through the whole stone in a nice regularity. I think this is also the reason for this slightly oily appearance in cut specimens.

I have something like this in mind for further processing
https://www.dreher-carvings.com/en/galery

I'm afraid I can't provide photos of the interior. I only have a Mini Cube immersion cell there and no microscope.


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 Post subject: Re: paperweight and potato
PostPosted: Sun Jun 07, 2020 6:59 am 
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@1bwana1
Yes exactly from the area are both stones

Karl Mpanga, former geologist of the mine from the beginning of the 60's until 2000, had shown us the original of this map, which he had drawn. The rough stone for the cut grossular I got from him. We had the opportunity to visit one of the pits. About 100 meters in diameter and 60 meters deep, funnel-shaped following the pegmatites in the serpentenite body.


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 Post subject: Re: paperweight and potato
PostPosted: Sun Jun 07, 2020 10:14 am 
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I was there the first time in the late 1970s, and a few time in the 1980s with some of the Greeks. It is likely that I met Mr. Mpanga there at some point.


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 Post subject: Re: paperweight and potato
PostPosted: Mon Jun 08, 2020 6:02 am 
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The world is a village indeed.


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