When I custom made my own shelfs, I used 16-inch wide slabs of marble with blue/gray viens, These shelfs are (6)feet long. Each marble shelf is,(1)inch thick,& there are five shelfs stacked about 18 inches apart, all the way up the living room wall,on a load bearing wall.
What holds these shelfs in place are, glass-dowel rods (hand-made/ blown),solid crystal glass. Each dowel-rod is two inches round & 18 inches long, & are spotted in equal lengths, across the whole 6-foot distance,on each shelf. Between these glass dowel rods & the Marble, I have rubber,Vibro-Pods on both sides sanwiched in between the rods & the White Marble.
The back-wall has solid oak, 2"X 2" trim pieces that are attached with wood screws to the studs in the wall.This runs the horizontal length of my walls,& holds up the back sides of this marble.
I also have two spot-lights mounted on track lighting, in my ceiling above these shelfs, they have black light bulbs installed. & At night, I turn them on, & Man!!! you should see how it lights up the white marble & shines like a spectrum through those glass dowl rods. Whew~Wee !!!!
Underneath all this marble shefing, is a poured slab of concrete about five inches thick. That way, you can dance, jump up & down & my Oracle Delphi Mark V Turntable, & my Benz Micro Glider cartridge does not even know that I'm in the same room.
How's that for permanent fixings ???