[Rockhounds] Darwin, CA Pyrite

[Carolyn Reynard]

Oh John,
I should have explained "cleavage flash". I'll bet you were surprised and
thought I was a bit bold. I had a good laugh over that one.

Different minerals break along their crystallographic planes. When you are
looking up a mineral in your mineral & rock guide such as Simon & Schuster's
Guide to Rocks and Minerals look for the notation about the mineral's
cleavage. Looking at Calcite's physical properties ...it reads ....perfect
rhombohedral cleavage... looking at orthoclase it reads... perfect 90 degree
cleavage.  I'm really not sure if "cleavage flash" is used with any other
minerals other than the Feldspars. The Feldspars really do this well. A
Feldspar's cleaved plane will give you a good reflection of light as you
turn the specimen in sunlight being that the Feldspars are vitreous on a
non-weathered surfaces.  This is not a crystal face but a cleaved surface
where the mineral separates along its crystallographic structure.

Now it would be interesting to find out if anyone else uses the term
"cleavage flash"...for minerals that is!

Still smiling..

Carolyn Reynard


----- Original Message ----- 
From: "John Siebel" <john at pandemoniumgraphics.com>
To: "Rockhounds at drizzle.com: A mailing list for rock and gem collectors"
<rockhounds at lists.drizzle.com>
Sent: Tuesday, December 02, 2008 8:55 PM
Subject: Re: [Rockhounds] Darwin, CA Pyrite


> Thanks Carolyn,
>
> But what is "Cleavage Flash"? When I Google it all I get is porn sites!
:-)
>
> John
>
> From: "Carolyn Reynard"
>  >Yes, you must dig out your hardness points and HCL to narrow down the
> > identification. Look for cleavage flash
>
> -- 
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