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Is this Phenakite?
  
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Andreu




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PostPosted: May 20, 2020 16:04    Post subject: Is this Phenakite?  

Hi,

I bought this specimen a few years ago in a mineralogical fair. I bought it as Londonite from Madagascar, but I think it looks rather like Phenakite. The crystals are completely white, while I think Londonite is rather yellow. Also the crystal form is completely different from the other Rhodizite crystals that I have. The matrix has some grey-greenish parts that in the photograph look more green that in reality. There is no fluorescence.

Can someone give me a hint? And I would also like to know what the matrix can be. Feldspar? Maybe Beryl or Phenakite also? It has like many layers of a somewhat transparent and light reflexive material. I have not been able to scratch it with Quartz.

Thanks!
Andreu
Barcelona



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Bob Carnein




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PostPosted: May 20, 2020 20:49    Post subject: Re: Is this Phenakite?  

Have you tested the hardness? (Is it harder or softer than steel or glass; try scratching the mineral (on a rough surface) and then try scratching the steel or glass.) Are the crystal outlines hexagonal? Does it fluoresce?
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Brent Lockhart




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PostPosted: May 20, 2020 22:59    Post subject: Re: Is this Phenakite?  

Hi

It is a bit hard to tell from the photo, but could it be something in the garnet group? Perhaps a pale Grossular or Andradite?

Cheers

Brent

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SteveB




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PostPosted: May 21, 2020 01:13    Post subject: Re: Is this Phenakite?  

Use a proper set of hardness scribes to test.

I think Brent is on the right track with a garnet group. Your crystals exhibit some crystal structure common to garnets but an imperfect symmetrical development. They seem elongated much like a large garnet I have in my collection, rather than the normally spherical dimensions. I don't understand crystal growth to know what causes it, maybe density and temperature changes of the solution during formation? I do have a white garnet also somewhere here which is very white, totally uniformly opaque.
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Jordi Fabre
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PostPosted: May 21, 2020 14:21    Post subject: Re: Is this Phenakite?  

To naked eye I would say Rhodizite. Some from Madagascar are colorless or white, but in this case, aside the tests recommended by the others, I'm afraid that the best to do is request an analysis of it.
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Andreu




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PostPosted: May 21, 2020 16:02    Post subject: Re: Is this Phenakite?  

Thank you all for your answers and suggestions!

Andreu
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