and did you know...??
The 'magic' ingredient for Pyrex is called Borax, and it nearly all comes from the one town of Borax in Southern California !
(I wonder how big THAT hole is by now???)
(at least according to my memory of some recent reading on the web, but I think it's correct!)
and I feel bound to point out...
The same sort of white effect can also be done to lead crystal or other sorts of glass, and is usually referred to as 'milk glass'. so please don't anyone think that ALL white glass is Pyrex or therfore ovenproof!