One of the most impressive looks for the fireplace available today is the 'cast stone' mantle and hearth. As the name would imply, this mantle and hearth system is usually cast in cement or plaster and comes in one color. White. While the look of the mantle is one of stone blocks complete with mortar lines and even divot imperfections in the stone, it looks like a white plaster cast. So the buyer is expected to somehow paint it to make it look like real stone.
Often a good faux finisher can be hired to make this mantle system look as it was intended. You might choose to have it look like marble, or granite. However the most often desired look is sandstone. This is also the easiest technique to reproduce.