Natural agate is one of the most jaw-dropping home materials out there, with eye-popping colors and arresting patterns that make it sought after by high-end clients who can foot the expensive bill, which is due to the painstaking fabrication process: Take grapefruit-size boulders whose interiors have turned to stunningly colorful crystals, tightly pack them into a steel box, toss in some crushed-up crystal boulder pieces for infill, pour in concrete and let it all set. Next use a gang saw to cut the slab into thin sheets, about 2 centimeters thick, chisel away the unsightly concrete, coat the slabs with epoxy resin, then polish the resin on one side to leave a smooth surface that's nearly 99 percent agate. A skilled artisan then must cut the slab to fit homeowner's needs in a way that allows various pieces to connect visually. All in all, agate surfaces can run up to $500 per square foot.