Friday, April 25, 2008

Varanasi ancient buildings made of Sandstones




Varanasi ancient buildings made of Sandstones.

By
Dr. Nitish Priyadarshi


From my childhood I visited the holy city of India Varanasi. Whenever I use to visit the Ganges river I always admire the big buildings on the bank of the holy river. I was always overwhelmed by the charm and structure of these ancient buildings. Most of the ancient temples and structures along the ghats have been destroyed. What remain are mainly 18th and 19th century buildings. According to the local people age of these buildings are more than 100 to 150 years. But they are still standing looking fresh as if it has been recently build up by the Maharajas. What fascinated me the most is the stones used in the buildings. All the stones were in the size of big slabs which are now not so commonly used. As a geologist I studied the rocks and it was found that most of the buildings were built with Sandstones. As compared to new houses and other houses these buildings looks more strong and weathered proof.

Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any color, but the most common colors are tan, brown, yellow, red, gray and white.

Some sandstones are resistant to weathering, yet are easy to work. This makes sandstone a common building and paving material. Because of the hardness of the individual grains, uniformity of grain size and friability of its structure, sandstone is an excellent building material. . In most sandstone used for building, quartz grains predominate.

Sandstone also has a long history in the building industry. The stone generally has a uniform texture and it is somewhat soft, making it a user-friendly stone for a variety of applications. It is favored for wall claddings because of its low absorption rate, high compression strength and aesthetically pleasing appearance. Its appearance and high durability make it ideal for flooring as well. With a variety of colors and finishes, it is also easy to match it to nearly any décor.

Massive sandstones consisting of closely interlocking and angular grains and free from structural defects was found best for building purposes. Most of the sandstones used in the buildings may have been supplied from Vindhyan System. The Vindhyan sandstones are fine grained in texture and available in abundance in a variety of colours like white, cream, and deep red and grey etc.

Vindhyan sandstones are regularly quarried in area very near to Varanasi in Uttar Pradesh.
The rock's formation occurs in two phases: The first is sedimentation, where layers of sand accumulate via water or air; the second is compaction, which occurs when pressure is exerted from overlaying materials and precipitation within the pore spaces between the sand grains. Sandstone is formed in layers and, over time, the layers become compacted until the bottom layers slowly turn into rock.

The stone is a common paving material because it can be highly weather resistant. Due to such quality these stone was used in mass scale in constructing stairs near the banks of the holy river. As a paver, sandstone is prized for its ability to maintain age and appearance over time, as well as for the different dimensions available. Sandstone pavers can be used for patios, pool surrounds, pool coping, balconies, as well as cladding and veneer.
The color of sandstone is extremely varied and depends on the quantity and color of the cementations materials present and the overall color of the mineral grains. Sandstone spans the full spectrum of colors, ranging from sandy yellows to deep golds, pale pinks and light greens.
Light colors generally result from the absence of cementitious materials, or joined by calcite or quartz. Buff, brown and red colors result from the presence of limestone and hematite. Greensand, a type of green sandstone, results from the presence of glauconite.
Dr. Nitish Priyadarshi
Geologist
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