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Spinel Group (Missing Members)

Posted by Daniel Helman  
Spinel Group (Missing Members)
September 04, 2012 08:54PM
Can you update the Spinel Group page, to include such members as are listed here:
http://tw.strahlen.org/systematik/systematik_oxide_b.html

Thanks!

Daniel Helman
Long Beach, California
avatar Re: Spinel Group (Missing Members)
September 05, 2012 12:25AM
    
Fixed.

But note that http://tw.strahlen.org/systematik/systematik_oxide_b.html also contains errors:
Filipstadite isn't true Spinel
Ulvöspinel photos on the site aren't real Ulvöspinel but rather Spinel itself. Ulvöspinel is metallic-black mineral.
Re: Spinel Group (Missing Members)
September 05, 2012 09:00AM
On my homepage (tw.strahlen.org) I followed the classification from the official IMA list
(http://pubsites.uws.edu.au/ima-cnmnc/IMA2009-01%20UPDATE%20160309.pdf)
In this list, filipstadite is placed in group 4.BB.05, the spinel group.

The ulvöspinel photos on my homepage are from a specimen, from which a crystal was taken for microprobe analysis and found to be ulvöspinel and not spinel. I think it is impossible to say just from a photo if a sample is ulvöspinel or not.

Thomas
avatar Re: Spinel Group (Missing Members)
September 06, 2012 01:32AM
    
Filipstadite was entered in the group list.

Thomas Witzke Wrote:
-------------------------------------------------------
> The ulvöspinel photos on my homepage are from a
> specimen, from which a crystal was taken for
> microprobe analysis and found to be ulvöspinel
> and not spinel. I think it is impossible to say
> just from a photo if a sample is ulvöspinel or
> not.
>
> Thomas

Dear Thomas,
I don't know who and how tested your specimen on microprobe. BUT, would you trust to somebody, who would show you light lilac transparent tabular crystal and tell you, that this is ilmenite?
Real ulvöspinel is opaque with metallic lustre mineral.
You may to send me 0.5-0.3 mm particle of your "ulvöspinel " and we'll look, how much aluminium it contains. ;)

Pavel
Re: Spinel Group (Missing Members)
September 14, 2012 05:35AM
Dear Pavel,
I made the analysis self (and you can be sure, I made in the last 25 years several 1000 analyses of minerals and other materials). There is no Al in this crystals above a trace level. And there is no exsolution of ilmenite in the crystals.
The crystals are completely opaque and with a metallic lustre in the inside. There is apparently just a very thin film on the surface that change the colour impression.

Thomas
avatar Re: Spinel Group (Missing Members)
September 14, 2012 09:32PM
    
Dear Thomas,
in such case these are great specimens, my congratulations!
But don't you think, that it would be good to state all mentioned above conditions in captions to these photos? Too many usual collectors try to "identify" their minerals only visually, using photos from databases. These photos aren't fit for such method, because colours and visual transparency of the mineral are reflected wrong.
Kind regards,
Pavel
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