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13 Dec-12:54:37 Re: need help determining what this is (John Betts)
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13 Dec-12:46:02 Re: minerals sans life (Pierre Joubert)
13 Dec-12:25:09 Need help determining what this is (Billclutch)
13 Dec-11:42:42 Re: prospecting pegmatite for schorl: need help. (Peter)
13 Dec-09:32:14 Re: collection of michael shaw (Crosstimber)
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Stumped, please help
  
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RobynM




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PostPosted: Feb 24, 2017 16:35    Post subject: Stumped, please help  

Hello All,
I'm new at this identifying game and I'm pretty stumped by this beauty. Here are some details...
Shape- doing, ball-like
Size- 1 in across
Texture - slightly bumpy
Color- overall color is grey but it is barker on one side than the other. When held to light, it looks like there is an underlying cream tone that comes through
Luster - non metallic

I appreciate any help you can offer.
Robyn



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crosstimber
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PostPosted: Feb 24, 2017 16:59    Post subject: Re: Stumped, please help.  

Hi Robyn,

Where and when did you obtain this specimen? It looks very much like a chalcedony concretion from Smara, Morocco. There were a number of these available at the recent Tucson Show.

A hardness test would be very helpful to determine if it is chalcedony, or something softer. Try scratching with a steel knife, which = 5.5, then try a known piece of quartz.

Michael
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RobynM




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PostPosted: Feb 24, 2017 17:41    Post subject: Re: Stumped, please help.  

Thanks for your reply, Michael.

I received this piece in a "mystery bag" from a gem shop in San Francisco so I'm unsure of where it originally came from.

Neither the knife nor quartz produced a scratch. Quartz left some mineral residue.

Might this be something that would reveal some additional beauty inside?

Robyn
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Peter Megaw
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PostPosted: Feb 24, 2017 17:43    Post subject: Re: Stumped, please help.  

Could be a similar beast called a Moqui Marble from Arizona. These are very popular with the healie feelie crowd and tend to show up in yard sales.
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Peter Megaw
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PostPosted: Feb 24, 2017 20:45    Post subject: Re: Stumped, please help.  

you are likely to be disappointed if you break it open.
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crosstimber
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PostPosted: Feb 24, 2017 20:50    Post subject: Re: Stumped, please help.  

RobynM wrote:
Thanks for your reply, Michael.

I received this piece in a "mystery bag" from a gem shop in San Francisco so I'm unsure of where it originally came from.

Neither the knife nor quartz produced a scratch. Quartz left some mineral residue.

Might this be something that would reveal some additional beauty inside?

Robyn


Robyn,

The fact that the knife blade and the quartz did not scratch your rock pretty well eliminates many possibilities. The fact that it is translucent, also points to chalcedony.
I agree with Peter - I don't think breaking it open will reveal anything fantastic.

Peter, I am not familiar with the moqui marbles from Arizona, but if they're anything like the ones from Utah and elsewhere, they are concretions.formed from sandstone particles cemented together by iron oxides. The ones I have are opaque, and fairly heavy for their size.

Michael
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RobynM




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PostPosted: Feb 25, 2017 19:26    Post subject: Re: Stumped, please help  

Michael and Peter,

Thank you so much for your insights. You've given me some material to look into. I'm leaning more towards chalcedony. The stone I have isn't gritty like the images of the moqui marbles I'm coming across.

I appreciate your replies!

Robyn
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