Have you thought why stone has been largely overlooked by the green building movement, while some products made of recycled plastic are regarded green??!!!

Stone is one of the earliest building materials. It is surprising that stone almost requires no special manufacturing processes and is so durable that stone structures built thousands of years ago are still used today!! (Very few contemporary “green” products may act the same in this case). Besides from that, stone has all the attributes of a green product. It requires almost no chemicals to produce or maintain, it emits no VOCs or hazardous airborne pollutants, and it is water-resistant. In areas with large temperature fluctuations, stone can play the role of a thermal mass. Also some stone even has good solar reflectance. Concerning biophilia concept, as buildings that connect people with nature, it is fair to mention the universal attraction of natural materials like stone. The truth is that stone is most natural material used by human being in the first place to accommodate our ancestors.

A life-cycle assessment (LCA) of granite and limestone claddings has shown that granite cladding compared to brick and mortar, precast concrete, and aluminum had the least detrimental environmental profile, followed by limestone, then brick (a virtual tie), and aluminum. In case of embodied carbon, sandstone, granite, and marble have lower amount than brick, timber, and steel (University of Bath’s ICE).

By comparing stone quarrying to a modest forestry operation, we can understand that the deteriorating habitat impacts are much less than logging and milling wood. Even the amount of site disturbance and soil and habitat loss from forestry operations far exceeds that of quarrying.

Stones that have not been crushed, called dimension stone, can be used as flooring, exterior cladding, solid surfaces, and interior walls, as well as for landscaping and many other applications. Moreover, the crushed stone can also be used in many other industries (concrete, asphalt, landscape, etc.) and this reduces its leftover.

Of the estimated 1.88 million tons of dimension stone produced in the U.S. in 2011, approximately 43% were used by the building industry. (For comparison, this figure is about 20% out of 95.6 million tons of total produced raw steel). Roughly half of the total U.S. stone market is imported from Brazil, China, India, Italy, and some other countries.

Stone Types and Uses

The primary types of dimension stone sold today are granite, limestone, marble, slate, and sandstone. (There are many others, including basalt, soapstone, and quartzite, etc.)

 Different quarries have different looks. Therefore, for designers and architects that search for a specific stone color or type, purchasing locally can be very difficult. Hence, the route that stone takes from processing to site can vary from a few miles to thousands of miles! Moreover, there are some stones that are imported from Brazil or another country and sent to Italy or China for processing before being sent to the U.S. Even stone quarried in the U.S. is regularly sent oversees for processing and then sent back to the U.S. This obviously wasteful practice is due to lower overseas labor costs. For sure, transporting stone from quarry to jobsite does have a negative environmental impact due to the need for heavy equipment and trucks transportation. A study of embodied carbon and natural stone shows that transportation is the main contributor of embodied carbon in stone. However, by considering the long service life of stone and its durability, those transportation impacts may not be quite as significant (in a 100-plus-year lifespan).

A major problem involved with stone is that tracking it from an extraction quarry to its final market can be nearly impossible since just like a commodity, both imported and domestic stone are often sent across the globe and may be processed elsewhere. This makes third party verification system unable to properly judge about some related issues.

There is a misunderstanding problem with stone quarrying. In fact, many people don’t distinguish between quarrying and mining. In mining a lot more material is taken out of mines than in quarrying. For example, in order to produce 1 pound copper, about 143 pounds of rock is needed. Furthermore, stone comes from rock which is at the surface and even at the end of a quarry’s production; the obtained area might be usable land in some cases (i.e. proper for lakes).

The point is although stone is not the greenest material or a complete one; it is close to some best materials that are considered sustainable. Most of the problems of applying it in construction industry are manageable. Therefore, it is essential to increase its valuable functionality in common belief by conducting some more well-organized researches in this case.

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