I also took physical science courses in middle school. Just because new stones are formed within the earth's crust at some marginal rate does not mean that they are considered a renewable resource.

Have you every watched a vulcano spit out lava?

I wouldn't call that marginal. And vulcanoes are just the visible part of that process happening everywhere in the crust.

We're talking about stone in general. Volcanic stone is one type of stone, which does not cover all of the applications of stone as used in buildings, masonry and other industries today. I also specifically addressed volcanic stones in a sister comment.

Some rate of formation is not enough to satisfy the commonly held definition of renewable resources. Google "is stone a renewable resource" for a jumping off point.