Masonry has held up buildings for ages. What makes you concerned? If the load actually isn't supported (and I'm 99 percent sure it is) your new beam would have to have its load transferred to the foundation which will likely take an engineer. Leave well enough alone or pay for a consult from an engineer.

Hey Brian, at that time just what you said happened, Yes the brick can hold but if take out chimney, you will need support. Show a photo if possible.

Ken

That is standard construction for a real masonry chimney structure. "Joist pockets'' in the masonry often support the roof. Why are you concerned?