Portland stone

Portland stone is a limestone from the Tithonian stage of the Jurassic period quarried on the Isle of Portland, Dorset. The quarries consist of beds of white-grey limestone separated by chert beds. It has been used extensively as a building stone throughout the British Isles, notably in major public buildings in London such as St Paul’s Cathedral and Buckingham Palace. It is also exported to many countries – Portland stone is used in the United Nations headquarters building in New York City, for example.

The term "Portland Cement" was coined by Joseph Aspdin who in 1824 patented a hydraulic binder created by burning a mixture of limestone and clay, resembling the previously existing Roman cement and presenting a texture very close to that of the oolitic Portland stone.

Portland’s freestone has almost certainly been used as a building material since Roman times. The many well crafted Roman sarcophagi (stone coffins and matching lids, hewn from single large blocks of Portland stone) that have been unearthed locally over the years, testify to the skill of their makers. It is interesting to speculate where the many large blocks of stone needed to make the sarcophagi were obtained and how they were transported.

It is possible that stones came from coastal exposures, where they may have been dislodged by the action of the sea, nevertheless the skills necessary to select suitable blocks, retrieve them, shape and hollow them are considerable and hint at an industry of some maturity. Were the sarcophagi "made to order" following someone’s death? Considering the amount of work and more critically, length of time involved, this would seem unlikely because of the practical need to carry out a burial promptly after death. Is it possible then, that during Roman times, there was a stone industry on Portland producing "off the shelf" sarcophagi?

The earliest known building to be constructed using Portland stone is Rufus Castle at Church Ope Cove, Portland. The original structure was probably built in around 1080, rebuilt in around 1259 and rebuilt yet again in about 1450 which is the likely date of the walls we see today.

 

Source: Wikipedia

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