[Rockhounds] Mineral ID

[Lawrence Rush]

While I am asking questions about the micas, let me try another one....

I recently got some "bi-colored" Lepidolite from Brazil, so- called because 
it has a darker colored purple "rind" covering the sides of the primary 
crystal faces, but still part of the crystallographic structure. The line of 
demarcation between the 2 colors is distinct. My question is: Would this 
likely be due to a change in the chemistry (or pressure, temperature, etc.) 
of the melt while crystallization occurred or is it an alteration that 
happened post crystallization?

Just curious......Larry


> Subject: [Rockhounds] Mineral ID
>
>
>
> Does anyone know the mineral species associated with the following
> aluminosilicate oxyfluorides? I have no reference work in which to find 
> these.
>
> The numbers following the formulas are the crystallographic pdf numbers
> ..................
>
> NaMg3AlSi3O10F2 - 25-0842
> BaMg3Al2Si2O10F2  - 19-0117
>
>
>
> Thanks......Larry Rush
>
> "Noel Coward thought work was more fun than play,  but he never, ever 
> worked in
> the mines"
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