That took me while to work out. You need to click on it and the click the stones on the bottom line to tell them to get back to work. Also, I just worked out that it takes a worker to do that. Also you can click market at the top and trade what you do have, e.g. iron for stone.
The stone quarry, it's the middle of the near row of buildings. The Zzzz coming up means they are not working in there. Hover over it and a green square will surround it then click.