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Staffordshire blue brick is a strong type of construction brick, originally made in Staffordshire, England.
The brick is made from the local red clay, Etruria marl, which when fired at a high temperature in a low-oxygen reducing atmosphere takes on a deep blue colour and attains a very hard, impervious surface with high crushing strength and low water absorption.
This type of brick was used for foundations and was extensively used for bridges and tunnels in canal construction, and later, for railways. Its lack of porosity makes it suitable for capping brick walls, and its hard-wearing properties makes it ideal for steps and pathways. It is also used as a general facing brick for decorative reasons. Staffordshire Blue bricks have traditionally been "Class A" with a water absorption of less than 4.5%.