The bricks above my mantle have white, patchy areas directly over the fireplace. Also, on both sides of the brick above the mantle, a white, sandy-like material forms in the mortar and falls off on the mantle. Is this a type of mold? My neighbor told me she has the same problem on her fireplace. What can I do about it? If anyone knows what this is and how to correct it, I would really appreciate your input. Thanks.