[Rockhounds] Blue Schist

[John Stockwell]

Adding to Pete's description/explanation, the term "blueschist," although 
glaucophane schist is the actual rock called by that name, is a metamorphic 
facies term, so we speak of "blueschist metamorphism," describing certain PT 
conditions. So not all "blueschist" rocks are glaucophane schists.

I was up at Jenner, CA two weeks ago searching for eclogite. Jenner is one 
of the "classic" localities for both rocks. I came back with blueschist 
(glaucophane schist) containing traces of eclogite (garnet and omphacite). 
The glaucophane schist itself is shot through with tiny garnets. There are 
one or two other mineral components, unidentified as yet, but no doubt from 
among the few commonly associated with blueschist.

I'll email the young lady.
----- Original Message ----- 
From: <Pmodreski at aol.com>
To: <rockhounds at lists.drizzle.com>
Sent: Tuesday, July 17, 2007 7:22 AM
Subject: Re: [Rockhounds] Blue Schist


>
> Hi Larry,
>
> I'll give an answer.  Blueschist (it's usually written as one word) 
> actually
> refers to a particular kind of metamorphic rock, glaucophane  schist. 
> This
> contains the mineral glaucophane, which is actually kind of a 
> bluish-purple.
> It's found in areas such as coastal northern California--the  Franciscan
> Formation.  Someone who lives in the S.F. Bay area and  knows about local 
> geologic
> sites would probably know how to obtain a  specimen.
>
> It's not really noted for good crystals, just a somewhat unusual
> grayish-bluish-purplish rock that is of interest to geologists. 
> Glaucophane schist
> occurs in metamorphic rocks that form in a somewhat unusual  environment 
> of high
> pressures and relatively low temperatures; in zones of plate  collision 
> and
> subduction (e.g., California!).
>
> Pete Modreski
>
>
>
> In a message dated 7/17/2007 8:06:19 AM Mountain Daylight Time,
> larryrush at worldnet.att.net writes:
>
> List: I  received this from a student in Fla. I don't know of any "blue
> schist", the  only thing that comes to mind is possibly a finely divided 
> kyanite
> schist. Can  anyone help her?
>
> Larry Rush
>
>
>
>
>
>
>
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