Clarifying the Geological Nature of Brazilian Metalutite

Dr Victor Cárdenes Van den Eynde, Petrology and Geochemistry Area, Oviedo University, has clarified his learned position in the recent discussion of metalutite.

Dr Victor Cárdenes Van den Eynde commented: “I would like to clarify some points in response to the article published in Roofing Today on 9 October on behalf of the Brazilian Slate Miners Association in reply to CUPA PIZARRAS’ discussion of the performance and durability of metalutite slate.

“From a geological and technical perspective, Brazilian metalutite is different from European roofing slate. This is not a matter of opinion: the academic and scientific evidence is clear, well established and leaves no room for doubt. Although Brazilian material is used for roofing and falls within the scope of EN 12326, it should not be considered equivalent to traditional European slates.

“European slates have undergone a higher degree of metamorphism, resulting in a more regular internal structure, cleaner splitting and higher mechanical strength. Brazilian material corresponds to metalutite, or low-grade slate, which retains sedimentary features that directly influence its performance.

“These differences are reflected in available ATG test results, which show lower bending strength and higher water absorption compared to European slates, particularly relevant in cold and humid climates.”

A more detailed technical discussion can be found here.

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