ATM "exotic" mirror materials

[chana@andr.UB.com (Allen Chan)]

Hi,

Has anybody worked with more exotic mirror materials such
as Zerodur or Sitall?  Here are some basic questions I have
about this these materials.

        1. How much would a 10 - 12 inch blank of these 
           material cost?

        2. How different is it to work with these materials?

        3. What is their 

                        coefficient of expansion 
                        weight
                        rigidity

           compared to Pyrex?

        4. Who carries these materials?

I heard that some people do not think too highly about Sitall.