Heat Treating

[JMLABRUM]

Heat treating makes some materials easier to work, but does that also mean that the stone is now weaker and more prone to fracture? Can stone also be heat treated to increase strength by quenching as is used in metals? I am working in the area of gun flints, but this would pertain to working arrow/dart points too.

[caveman2533]

for gun flints you do not want to heat treat your stone. The edge will be more brittle cause it to dull faster scraping across the frizzen.  For arrow points is not such repeated abuse. If you heat  and quench you will have nothing but fish tank gravel left after the quench.

[Zuma]

Like caveman says,
Raise and lower your heat slowly. Don't try a Raku method.
Just a slight draft of cooler air can shatter the stone while cooking it.
It's all about the atomic structure. 
From my experience with English flint, I find the glassier translucent
parts of the flint will not tolerate to much heat but the lower grade
materials need it for making points.
Zuma

[Dalton Knapper]

I've made several hundred gun flints and it's a fact that you do not want to heat threat them. Only raw rock will do.

No type of chert, flint, etc., etc. can be heated and quinched - it just fractures into little pieces, as others have noted.

[JMLABRUM]

  Thank you amigos. You have saved me much trouble.