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Advertising supplement provided by The Marble Institute of America

How savvy are architects at specifying stone?

"Some of them---like SOM, HOK, Pei Cobb Freed & Partners, and Kohn Pederson Fox, have become very good at this; some are still learning," Swindal says.

Those who are talented, he says, insist, first of all, on substantial testing, and, secondly, routinely meet as a team (owner's representatives, designers and contractors) with quarry managers and fabricators to ensure that stone is available in a timely manner, that material to be quarried has not been committed elsewhere and, most importantly, to specify color ranges and allowable occlusions in selected stone.

"You can't make these decisions based on a two-inch square of material in your office," he says. "A plant and/or quarry visit is essential. But before I do that, I have asked the supplier for one-foot, or two-foot samples indicating the likely range of the stone for identification. The fabricator may have been working this particular stone for the past six months and may know it very well. Review the stone in both morning and afternoon sun. Tell the fabricator, 'Show me what you expect and what you will guarantee in terms of range of color.' It may take two slabs; it may take four; it may take 20 to represent the range of the material and possible alternate finishes: A polished finish shows off the stone's character; a thermal finish is more forgiving and softens the look of the stone."

On large projects where 100,000 to 200,000 sq. ft. of stone is called for, a mock-up of the building, conducted at the fabrication plant, is essential, say industry consultants. "Sometimes the architect will send the glass to be used on the project, to see how the windows, the spandrels, the stone interact," says one. Experienced architects will ask "Will all the material come from the same location in the quarry?" If not, its characteristics may vary significantly.

Stone may contain occlusions the size of a fist. It depends on the material. The architect may say he or she wants occlusions no bigger than the size of a dime. The fabricator will sometimes say he say he can't meet that demand. Notations by the inspection team on the back of sample slabs specify, and commit the fabricator, to acceptable occlusion limits and acceptable color characteristics. Thermal finishes, if not done right, can look wavy. Granite, if cut radially (across the grain of the stone), can have a very different appearance. It is critical that such details be agreed upon before fabrication begins.

Most U.S. stone suppliers and consultants still rely primarily upon European stone. Most have full-time agents in Italy, Spain, and elsewhere, who negotiate with quarry owners and fabricators to ensure that U.S. construction standards will be met.

Of other emerging markets, one consultant says this: "I have bought material in China, but it is a difficult source to work with. Construction methods are not up to date, and although the quality of the stone is fine, you are working with a Third World culture in which there are problems getting stone extracted and manufactured to our specifications and delivered when we need it. It is important to have trusted relationships in this market, like those we have with Europe, Argentina, or Brazil."