When I learned earlier today that it was in fact a Limestone, I still felt that it was correct to distinguish it from the Limestone quarried to manufacture concrete, as I alluded to in an earlier post. It is not simply a question of regional variation in the naming of a quarried product, but totally different end use of that product.
I see what you're getting at and I agree these specific names are often well known so it would be good to include them, but perhaps the 'Bath Stone' or 'Bluejohn' could go in the also-known-as field, at least then they would show up in a search.
The problem about separating things out by purpose, in my view, is that Building stone can be granite or sandstone as well as limestone.
You could set up a category for building stone but then, as johnnym says, why not roofing slate? Limestone can be used in a number of different ways.
For its chemical properties eg calcined for steelmaking, or for agricultural lime or for cement;
As aggregate for roadstone or concrete;
As building stone;
As ornamental stone.
Do they all get a category?
To complicate matters further, limestone from the same quarry may end up being used for several of these different end uses.
There are 10 types of people in the world.
Those that understand binary and those that do not!