Kentish Ragstone in Rochester

A sample of Kentish ragstone from Rochester city wall

During both of my visits to London at the end of 2016, I had encountered various examples of Kentish ragstone and Reigate stone in the Tower of London, All Hallows by the Tower, the Jewel Tower, Westminster Abbey and in the parish churches of Bromley and Beckenham.

The geology around Rochester and Maidstone

I finished off my last trip with a day out to Rochester, where I had plenty of time to explore its castle, cathedral, city wall and other places – all of which make good use of the Kentish ragstone that was first floated downstream along the River Medway from Maidstone and Aylesford by the Romans in the 2nd century AD.

The north-east bastion of Rochester city wall

As a geologist with experience of the building restoration industry in London, and having developed an eye for stone identification and matching, I had only seen these grey/green glauconitic building stones in passing. I had always thought that the hard and brittle nature of Kentish Ragstone made it suitable only for rubble walling and that it was only Reigate stone that was used for ashlar, quoins and other dressings.

A section of Rochester city wall off High Street

In developing my own interests in building stone, I had followed in the footsteps of geologists such as Eric Robinson and Francis G. Dimes but, never having the opportunity to work on the royal palaces or similar buildings during my time in London, I didn't take much notice of the work of Bernard Worssam and Tim Tatton-Brown – a geologist and archaeologist/architectural historian respectively who have contributed to the work on various royal palaces.

Kentish ragstone from the south-west bastion of Rochester Castle

Both would be considered to be experts in both Kentish ragstone and Reigate stone, having extensively researched their quarrying, distribution and use and identified variations in the lithology and petrography that only professionals with specialist expertise would recognise.

Restoration of a Kentish Ragstone wall on Castle Hill

During my wander around Rochester, I discreetly collected samples from various walls, including new stone that was being used to restore a wall near the castle. I don't have a microscope and have to rely on my own eyes, a hand lens, hydrochloric acid and a steel knife for my investigations, but I now have a better understanding of this material.

Kentish ragstone from the Hermitage Quarry used on Castle Hill