[Rockhounds] Mineral ID

[Lawrence Rush]

Thanks very much, Andrew! Good answer!

Larry

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----- Original Message ----- 
From: "Andrew Turner" <turnea55 at hotmail.com>
To: <rockhounds at lists.drizzle.com>
Sent: Friday, March 07, 2008 8:19 PM
Subject: Re: [Rockhounds] Mineral ID


 The lithium mica (e.g. lepidolite) phase diagram has something like 17 
separate end members (I used it as a cover for a paper I did in phase 
equilibria class).  This means that there is technically some 17 different 
dimensions to the diagram, good luck on the visualization and modelling.  It
 takes very little changes in temp., pressure, or chemsitry while the 
mineral  is forming to cause lithium (or any) mica to have a different color 
and/or  slightly varying chemisty, even to make it a separate species. This 
is  common for many pegmatite minerals due to how they form and how many of 
them  are "trash can" minerals in that they can accept numerous different 
elements  into their structures (check out the tourmaline or the 
ferrocolumbite-manganotantalite series.  Yellow, purple, and pink lepidolite 
can be found together.  I even have some pieces from South Dakota that are 
half biotite and half muscovite (a small reaction zone of possible 
phlogopite is seen at the contact).  Hope this helps.

 Andrew Turner
 Victorville, CA USA