Borosilicate glass -- easy fracture?

I was under the impression -- perhaps false -- that "Pyrex" and other
borosilicate glasses didn't fracture as easily as natural untempered
glasses, but a light impact resulting in a very sharp concoidal sliver
from the inside rim of one "ovenware" top that we have made me think
again. Isn't most "ovenware" tempered? I know tempering is an entirely
separate consideration from composition, but are untempered
borosilicates any more or less apt to fracture or shatter than regular
glass?

TIA
Mark 'Sporky' Stapleton
Watermark Design, LLC
www.h2omarkdesign.com
.