I imagine that there are good sources of ash closer than you think, and tuff is all over as well. Tuff is simply consolidated volcanic ash. It’s usually a soft rock, easily worked.
Of course, environmentalists would scream about digging out even something as common and worthless as volcanic ash. They make enough noise about digging out sand for glass, even.
No tuff here-but no shortage of rocks-the whole area is limestone and was a sea bottom-there is a pricey product called Austin shell limestone that contains pretty snail fossils-it is cut into bricks and used for facades of homes...