Between five and ten years ago granite counters were make with steel reinforcing robs under the front and back of the sinks rails. This was done to stop the granite from cracking during installation. Over time the caulking can break down and water can reach the steel and cause it to rust. Rusting steel expanse and cause the granite to crack like in the pictures. In most case the crack can be fill but it still look like a crack or the counter has to be replaced. We have the solution we can replace the sink and cut away the crack granite with out replacing the count.