The advantage of sealing your stone mantel is that it will be much easier to keep clean. For example, should a child write on it with a crayon or someone was to spill coffee or wine it can easily be cleaned.
Although we recommend a specific brand of sealer, any good quality clear stone sealer will work. We suggest a product made by Chemprobe Technologies, Inc. (800) 760-6776 called Prime-A-Pell 200 which is a clear, filmless, penetrating water repellent that comes in both water-based and oil-based applications. The treatment does not alter the color or texture of the surface, nor significantly affect the vapor transmission qualities of the substrate. The solution penetrates the substrate and chemically reacts to create a powerful barrier against water penetration. This barrier is resistant to ultraviolet and weather deterioration. It is easy to use and should be applied to a clean, dry surface. Apply it with a foam-tip applicator, not a bristled paint brush. Thoroughly saturate the stone almost to the point of running. Drying time is 6-8 hours.