Kimmeridge
Crucibles made of fine textured white clay which the author says brings to mind the white pipe-clays of the local Dorset, Bagshot, Beds.
chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://historicengland.org.uk/research/results/reports/2977/NOTEONTHEPETROLOGYOFSOME17THCENTURYCRUCIBLESFROMKIMMERIDGEDORSET
Source: Note on the Petrology of some 17th century Crucibles from Kimmeridge Dorset, D.F.Williams PH.D., F. S. A. (Department of Archaeology, University of Southampton'.
I hope the link to the author's paper works - I couldn't find any other way of doing it.
A little more information here on a Clavells Glasshouse in Kimmeridge:
https://unpathd.ads.ac.uk/resource/d7468acc56ce01e657a52bcd5e6741591ab57d35e52c7c19dfcd3a557891c131From a small snippet of information I saw but couldn't access, Robert Mansell might have been involved here?
More:
It seems glass was produced there with an agreement from Mansell? Furnace built by Abraham Bigo and Sir William Clavell
https://www.tandfonline.com/doi/abs/10.1080/00665983.1987.11021206Could this have been a link with Philip Foote? Clay from Purbeck?