Many of you probably recognise chalk – it has long been used for drawing with! But chalk is not the only useful type of limestone! There are many other uses for limestone, and one of them is for building with!
There is a small island off the south coast of England, called Portland.
Most of the Island is made up of limestone, called Portland Limestone. This is a very high grade limestone, very good for building with. In fact, you may have seen some, even if you have never been to Portland! You see, when St Paul’s Cathedral needed rebuilding in 1661 after the Great Fire of London, Sir Christopher Wren decided to use Portland Limestone!
After this, Portland became ‘The Stone of London’, and many important buildings and monuments are made of this limestone, such as The Cenotaph in Whitehall.
There is another building stone that comes from Limestone – cement! It’s true! You get limestone, grind it up, bake it to extract any water, and then you have powdered cement. Mix it with water and you get instant rock – Cement! This shows you that limestone formation can happen quickly – it’s all about process, not time!
There is also a building rock that comes from limestone, but is not actually limestone – marble. Marble has been revered as a beautiful building stone for many years, and is often used as fireplace backgrounds and for large building columns. Marble is from limestone, but once it has gone through metamorphism. This is when the limestone has gone under large amounts of heat and pressure, changing the chemical structure of the stone into a crystal – marble!
One final rock that also comes from limestone – flint! Again, not limestone, but needs it to form. Flint is when the silica from the shells that are fossilised in the chalk gets extracted, and then, due to a chemical reaction, solidifies into a very strong, glassy rock. Flint has been used for building for millennia, particularly in Saxon and Norman churches around East Anglia and the South-East.