Ten shafts lined with slabs of tufa which were there found may have been the approaches to tombs or may have served as wells.
The hill on which Sessa lies is a mass of volcanic tufa.
Calcareous tufa or travertine occurs in the valley of Matlock and elsewhere, the southern part of the county, from Matlock southward by Heage, Belper and Duffield to Derby.
Calcareous tufa or travertine occurs in the valley of Matlock and elsewhere, and in some places is still being deposited by springs.
by abrupt tufa cliffs; but a massive wall found by excavation on the S.W.