A wide dispersion LCR mounted right to the stone fireplace would work well. From my ATC world, a SCM 12i which has a steel plate to mount to in the back and Adaptive Technology stuff to use as the "arm" to the bracket. This is how studios and post houses do it. You'll need a serious hammer drill to lag bolt into the stone. You need a bracket that can be tilted downward to keep energy off the glass.
Wide dispersion for sure horizontal, but narrow vertically.
Wide dispersion for sure horizontal, but narrow vertically.