I think getting a useable stone has more to do with mining (quarrying) than masonry (in effect, sculpting). I think miners would know all about different methods of stone extraction. Did Michelangelo quarry his own marble?
Well, maybe. I'm just thinking that miners know how to break rock, while masons know how to work and extract it without chipping it. There's a difference working with sledges and picks over working with hammer and chisel.
I can't imagine that you can even accidentally produce sculpting material from just normal mining, which more or less focuses on chipping the heck out of a solid wall of rock and keep going. Heck, in real life only some types of rock are even workable like DF stone is, and they require careful extraction.
That said, i believe that maybe you're right. But i again stress that the designated tasks should be different. Extracting rock versus tunneling through it may demand the same skills, but have entirely different intentions behind them.
I'll not get into skillsplitting...
Ex.
mining - rockworking(100)
masonry - rockworking(50), furniturecrafting(50)
stonecrafter - rockworking(50), craftworking(50)
woodcutter - woodworking(100)
weaponsmith - metalcrafter(50), weaponworking(50)
smelter - metalcrafting(100)
bowyer - weaponcrafting(50), wood/boneworking(50)
Well crud.
Anyway.. tasks could use two skills, half exp from both. One for the material used, and one for the category of item. A lot of similar professions could be made redundant this way.
Materials: Wood, bone, scale, metal, leather, cloth etc.
Category: Furniture, crafts, armor, weapons etc.
That way, miners would know a great deal more about masonry than just another peasant, and your armorsmith can fill in for the blacksmith easier whenever that thing happens that kills him.