XVI Reunión Científica de la Sociedad Española de Arcillas - Libro ...

Silva J et al. / Comunicaciones SEA 2001 – Baeza (Jaén)
alteration of both glass and alkaline feldspar existent in tuff (Silva et al. 2000). It
occurs in very small contents in tuffs from the original quarries, however, the
alteration proceeded rapidly after Cathedral construction. In the altered building
stone the fine platelets of smectite are assembled forming face to edge or cardhouse
structures (Figure 1). Volume increases due to the development of these
aggregates and volume variations due to changes in humidity diminishes
intergranular cohesivity in the building stone producing powdering and spliting
(this pathology being favoured by the textural anisotropy exhibited by the tuff).
Acknowledgments
Authors thank the support provided by CITMA (Centro de Ciência e
Tecnologia da Madeira), Secretaria Regional do Turismo e Cultura (DRAC) e
Fabrica da Sé.
Figure 1. Smectite exhibiting card house structure (7000X) found in weathered red lapilli
tuff from the Funchal Cathedral.