The slates are quarried near the village of Collyweston in Northamptonshire, near Stamford and close to the borders of Lincolnshire and Rutland. Traditionally the mined stone was left outside for three winters until the frost revealed layers that could be broken ("clived") into flat slates.
In the late 1990s, English Heritage (now Historic England) worked with the Burghley Estate and Sheffield Hallam University to develop an artificial system to reproduce the freeze-thaw cycle needed for production of slates. In 2012, when new slates were needed to reroof parts of Apethorpe Palace, further testing was commissioned by English Heritage to develop the artificial frosting and new Collyweston slates have been produced. New slates have been used to repair the roofs of Ufford Church in Cambridgeshire and High Wycombe Guildhall.
In 2015 a planning application to reopen a slate mine in Collyweston was approved; the slate mines had not been used since the 1960s. Slate from the mine will be used to repair Bodley's Court in King's College, Cambridge, Clare College, Cambridge and Old Westbury Gardens in Long Island in New York.
- "Commenting on Collyweston stone slate".
- "Case study for Heritage Counts 2015" (PDF). Historic England. Retrieved 10 January 2017.
- "Collyweston slate mine set to reopen after bid approved" BBC News 16 June 2015
- "Mine re-opened after 50 years for work on King's court". Varsity. 24 December 2016. Retrieved 10 January 2017.
- "The small English mine helping a famous US mansion". BBC News. 27 January 2020. Retrieved 27 January 2020.
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