[Rockhounds] Garnet & Kyanite

[Carolyn Reynard]

I would love to collect on Freezout Mountain.

Very often here in Dutchess County, NY [where we have a classic metamorphic
sequence from the Hudson River to Connecticut ] we find the garnet and
staurolite together. What I find fascinating is these minerals have the same
chemical formula; the crystal form changes with the increase of temperature
& pressure. There is very little kyanite here and the sillimanite is
microscopic. Even further east into Ct. one finds both greater metamorphism
[ where the kyanite was located in original e-mail posting] and actual
melting of the rock forming some very fine pegmatites.

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: Monday, November 05, 2007 8:18 PM
Subject: Re: [Rockhounds] Garnet & Kyanite


> Freezeout Mountain, Shoshone County, Idaho sports both kyanite and garnet
in
> mica schist. There is staurolite nearby. Lanny could certainly elaborate
on
> this as his field guides got us up there.
>
> John
>
> ----- Original Message ----- 
> From: "Carolyn Reynard"
> Kyanite forms at a higher pressure and temperature than garnet, so usually
> they are not together. There are exceptions I have a specimen from Russia
> that has both. I believe that would indicate my Russian specimen is right
on
> the boundary ( isograd) between the two. (adjacent metamorphic zones on a
> map are separated by isograds or line of equal grade.)
>
>  Not sure about the alteration of kyanite to mica, but I do know
cordierite
> alters to mica, so there is a good possibility. Kyanite is often found
mica
> schist.
>
> Carolyn Reynard
>
>
> -- 
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