Marble, limestone, slate, travertine, granite. These surfaces are everywhere in new homes these days, from countertops to entry foyers, around fireplaces, in bathrooms and in kitchens, as wall accents in formal living spaces and underfoot on elegant indoor/outdoor patios. They come in rough hewn, glassy, satin buffed, or pitted varieties. We are bewitched by the enduring beauty of these natural geological surfaces, and realize that mankind has been using stones in building since the beginning of recorded (and unrecorded) history.

Perhaps because of the wealth of synthetic materials we have been introduced to over the years, we seem to gravitate back to what came naturally to begin with, and value it even more. Back in the 60's, stone- look surfaces were imitated with melamine on countertops, appearing amazingly real from a distance. Upon closer examination, the edges seemed too square, or the shine appeared a bit too plastic, and the tap was definitely hollow under our fingertips. In later decades, stone-copying Corian countertops came into vogue, still popular today.

What these materials set out to imitate, however, was a natural product. There is beauty in every use of stone, and discovering that beauty is practically becoming a new art form in new home construction and enhancement. Even though the cost of natural stone is considerably higher than that of ceramic tile, it seems to be where many homebuyers, even in smaller homes, seem to putting their upgrades dollars. One of the most enduring surfaces available, stone is easily cleaned, and is considered by many to be a form of natural art.

Perhaps we should begin by defining a rock. According to Alpha Granite and Marble (www.alphagranite.com) , a large stone product distributor on the West Coast, a rock is a hard substance composed of minerals, typically more than one. Each type of rock is formed in different ways; igneous, sedimentary and metamorphic. Igneous rock (commercially called granite) is formed by the hot, fluid magma that moves within the earth's crust. Rock considered sedimentary is composed of particles that have been carried along and deposited by wind or water. Over time they become pressed together to form rocks. Metamorphic rock is formed when chemical reactions, heat, or pressure, or a combination of these, forces existing rock into new kinds of rock. The new rocks have different physical and chemical properties from the original rocks. Organic rocks come from living organisms. Limestone is often (but not always) made from organic rock. Deposits of limestone are typically derived from the shells of creatures such as clams and certain microorganisms. Limestone, onyx, and travertine are all in the family of organic rock.

In the stone industry, rock can be classified by geologic classes or groups. Geologic class describes the ways in which a rock was formed; groupings take all mineral-based, igneous and metamorphic rocks such as granite, and the calcite-based, organic rocks as calcareous stones. Granites are typically harder, denser, and more durable than calcareous stones, which are more vulnerable to common domestic acids, such as orange juice, milk and vinegar.

Many homebuyers considering the use of natural stone ask whether marble, limestone, travertine, and onyx are porous, vulnerable to staining, water absorption, and scratching. According to the Alpha Granite experts, the answer is technically "yes" and practically "no." Practically speaking, porosity is not significant as long as the stone is properly sealed to resist water, oil, and contaminants. All stones are subject to scratching. Organic stones, such as marble, limestone, travertine and onyx scratch more easily than a mineral stone, such as granite; thus the popular use of granite slabs in countertops for kitchens and restaurants.

Fine stone is extracted from quarries on 6 different continents and from some islands as well. Blocks are cut out of the mountainside walls using drills or wires with abrasives embedded in them. Most blocks are about the size of a mini-van and weigh about 50,000 lbs. each. They are graded according to color, movement, structure and overall appearance, with some reserved for slab or tile production. Those with structural or aesthetic problems are destined for road-building, cement-making, or even water filtration. The graded blocks are then sold to stone-processing factories around the world. The blocks are cut into more manageable pieces by a huge machine called a gang-saw. The slabs are then inspected, prepared and polished through grinding wheels to create a shine. Stone tiles, of course, are created by cutting the blocks into thin strips and polished and cut into squares.

Understanding the millions of years of dynamics that go into stone formation can add depth to your appreciation of this wonderful material, and perhaps makes its use more meaningful. When considering the use of stone materials in your new home, ask as many questions as possible to gauge where certain stone surfaces are best used for the longest lasting beauty and effect.

Published: April 7, 2000

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A veteran of the real estate and homebuilding industries since 1986, Dena Kouremetis first joined Realty Times as a new homes writer in 1998. Since then, she has authored four books, written consumer columns on new homes issues for websites and newspapers all across the country, contributed to builder trade magazines, appeared as a guest expert on several radio shows and even created a ten-chapter podcast for LendingTree.com’s homebuilder website, iNest.com, now available on iTunes, entitled Uncharted Waters; Navigating the Purchase of a New Production Home. Kouremetis recently joined her local Folsom, CA Coldwell Banker office as a broker associate while continuing to write for the real estate industry. For the past three years, she has been training real estate agents for both the resale and new homes industries, putting her experience, research expertise and gift of expression to work to help others entering the business.