Here, in Virginia, we are blessed to have the best axe and celt stone around, in fact the only location where the greenstone is knappable, however, we are not so lucky when it comes to rock for other things such as points and knives, though they an be very sharp (occasionally sharper than chert/flint) and are very durable. Basically, I am trying to say is that we have a lot of tough stone to work with, and we make what we can (or they did), and in particular, quartzite. All quartzite is grainy, and can be heat treated. However, though it can be heat treated, it mostly affects the color, and does not often make a difference in workability from what I have read, but is has been stated that it can effect the workability in terms of elasticity, meaning it crumbles more. I hope this helps, I figured I could relate to your post due to the topic of heat treatment on tough and grainy stone. One of the things I love about primitive skills is that it takes experience to learn and become better, so could try and heat treat it, though it can be difficult.
"It's about what you learn, not what you make" - Erret Callahan
"Win some, lose some, and sometimes ran out" - Kenny Roberts