Hi TB,
We do not recommend mounting your TV over a fireplace. Your primary concern will be the heat; Samsung TVs should never exceed 104°F. Before you even think of mounting a TV above your fireplace, light a fire and check the temperature first.
If you have a wood-burning fireplaces, ash could accumulate on the TV and its vents. You may be cleaning the TV much more often because of it.
Also keep in mind that if you mount your TV above a fireplace, it will be well above eye level when you're sitting down. Consider getting a mount that can be angled to make it easier on your neck.
~ Samsung Advisor