Fig. 8

Ternary plot showing relationship between proportion of opal CT, calcite and clay (cementing components of stone), sorption hysteresis at RH80, and pulse velocity. Hygro-physical properties selected to represent performance of stone. One sample from each quarry deemed most suitable for building stone selected. Limited number of high calcite stones shown to perform well. Thirteenth to fifteenth century stones are relatively higher in clay content and perform poorly. Other stones with variable performance