[Rockhounds] Puzzle

[Lawrence Rush]

Carolyn: According to my Kraus, Hunt, and Ramsdell "Mineralogy", a partial 
exchange of some mineral constituents (such as Chlorite after Garnet) is 
called an "Alternation Pseudomorph". But the replacement material has the 
chemical properties of the new mineral, not the old, and the same form.

I can't find any pseudomorph described where the hardness still exists for 
the replaced material, not the replacing one. In this case, I take this to 
mean that your hardness should reflect that of the feldspar, not the Beryl, 
in the replacement material. But, this text is almost as old as me, both of 
us need some updating!!

Comments from the experts????

Larry


----- Original Message ----- 
From: "Carolyn Reynard" <sunstone33 at verizon.net>
To: "Rockhounds" <Rockhounds at lists.drizzle.com>
Sent: Sunday, July 12, 2009 2:45 PM
Subject: [Rockhounds] Puzzle


To the List: I have and interesting puzzle.

I collected the specimen at the Havey Quarry, Oxford Maine.

It is a crystal that appears to be common beryl as you can determine the 
hexagonal crystal shape.  The hardness is
7.5.  The color is a warm light tan.  The matrix is feldspar.

What doesn't quite convince me it is a  beryl is a texture that looks likes 
like perthite and runs the complete length of the crystal into part of the 
matrix and is at right angles to the C axis. The feldspar matrix fluoresces 
at bright light blue with red perthitic texture as does this crystal..

I am wondering if this specimen is a pseudomorph, with perthitic microcline 
after beryl.   Would the microcline replacement still retain the hardness of 
the beryl?

I believe this is the important question.  Certainly the crystal fluoresces 
like the microcline  but there is the problem of hardness being too great 
for a feldspar.

Nice specimen, just wish I could figure it out!

Carolyn Reynard



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