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It's three sizes of Vintage Vein travertine from Materials Marketing - 2x9, 3x16, and 4x24. The stone has veins that range from tan to taupes to pale gray. It's got very versatile coloring. I have used it in tan, gray, and beige color schemes.
The designer here has chosen a stark and simple concrete fireplace surround, then warmed it up via the natural light, wood tones on the floor and furniture. Upholstered pieces and an area rug softens it up. Bravo!
Here's a more Old-World stone mantel and matching stone (I'm guessing limestone or travertine). The hearth is raised off the floor and the slab material continues throughout the design.
I don't remember exactly what this was, but believe it was just a 12x12 Crema Marfil marble, available at any tile store
that is a pre-cast concrete facing
The mantel is limestone and was fabricated by Alkusari Stone in Austin. It was sealed with a tinted penetrating sealer.