[Rockhounds] Mica Progress Report - Pictures

[Gary Brown]

Thanks, Jim...  That makes sense.  I knew it was going to be something in
the bonding, but being WAY removed from my old chem days (and my UofMn chem
major son was somewhere else!) I couldn't quite nail it.

And to all...

Thanks for the kind words on the piece.  I'm getting another set of
responses over on the "glass" groups I belong to.  It's fascinating seeing
how two different groups are looking at this.  Mind you, the glass folks
aren't just blathering on about aesthetics!  There is a LOT of discussion
about the physics of what is going on in terms of glass/mica bonding and
physical distortion during the slump process. There are folks over there
that are doing $10,000 - $20,000 commissions.  When they put $5,000 of glass
into a kiln they HAVE to know what's going on!

I'm going to put a fairly good sized sheet, probably around 4-5cm, between
some glass and then try to do what's called a "drop slump".  That's where
I'll lay the glass over a whole in a mold and let the middle "drop" down
around 4-5cm.  I'll be interested to see what both the glass and mica do.
Will the mica stretch?  Will it solidify and then blow up in a day or two
due to accumulated stress?  

GcB
 

> -----Original Message-----
> From: rockhounds-bounces at lists.drizzle.com 
> [mailto:rockhounds-bounces at lists.drizzle.com] On Behalf Of 
> Jim Murowchick
> Sent: Saturday, October 20, 2007 3:08 PM
> To: Rockhounds at drizzle.com: A mailing list for rock and gem 
> collectorsgbrown at catspaw-minerals.com,
> Subject: Re: [Rockhounds] Mica Progress Report - Pictures
> 
> Gary-
>     Mica is a hydrous mineral, and contains OH groups, and 
> often some water in the interlayer sites.  Heating can cause 
> the water to separate the structural layers (heating 
> vermiculite, causing it to expand, is an extreme example of 
> this).  The expansion probably disrupts the ionic bonds 
> between the interlayer potassium ions and oxygens in the <snip>
> 
> Best regards,
> Jim Murowchick