The fireplace surround is made using reinforced concrete. The striation you see is from the form used when the concrete was poured.
Here is a featured ideabook that expands on that subject more thoroughly.
tv and fireplace on one wall
next house project love the fireplace
Side by side tv and fireplace?
offset height of tv from fireplace
Off center placement of wall hung flat screen TV and fireplace on
absolutely hate when tv competes w/ fireplace... love the finishes.
floor to ceiling tile for fireplace
for your fireplace surround, try a gray-colored tile to create the same effect.