The stone tiles used was a natural slate with a mixture of several different colors of autumn, green and multi. Detroit's Pewabic tile was also mixed in with a variety of patterns and colors. www.pewabic.org
The same 4x4 tiles could be used for the hearth or larger pieces of slate. Concrete slab for a more contemporary look or soapstone is an option. Though I have not seen your space, so there may be other options that work better.

Thanks for the info!!

What was the brand and color of the paint?

I believe we used Benjamin Moore Pale Sea Mist 2147-50.

Beautiful fireplace. Please describle the mantel top and the legs?

Thank you. The surround has a mixture of painted and stained cherry with Arts and Crafts details in the trim accents. The mantle top is solid cherry with a stain. The legs are a cherry veneer stained. Hope this helps.