A heritage stone of Rio de Janeiro (Brazil): the Facoidal gneiss

Abstract

This paper presents the Facoidal gneiss, the most significant and characteristic natural and heritage stone of Rio de Janeiro, Brazil, also known as 'the most carioca of rocks. ' The metropolis that is a World Heritage Cultural Landscape was built on, over, around, and with local stones, mostly Neoproterozoic gneisses. Among them, Facoidal gneiss occurs both sides of the Guanabara Bay, shaping its natural monuments as the Corcovado and the Sugar Loaf. It is composed of K-feldspar megacrysts usually deformed, looking like eyes (augen), arranged in a quartzfeldspar and biotite rich matrix. Its colour varies from pink to greyish. This stone was substantially used as a building material in many heritage monuments and buildings, in frames of windows and doors in houses, in sidewalks and public infrastructures. The aggressive environment of Rio de Janeiro, a tropical coastal megalopolis, is reflected in decay patterns such as loss of matrix and spalling. There are no quarries in production as this rock outcrops stand inside nature conservation or urbanized areas. The current impossibility of extracting replacement material justifies calling attention to this stone for the better conservation of Rio de Janeiro's built heritage.

Building Granite Characterisation, Construction Phases, Mason’s Marks and Glyptography of Nossa Senhora de Guadalupe Church, Mouçós e Lamares, Galicia-North Portugal Euroregion

“…In the frame of this new interest, the concept of Heritage stone (Cooper 2010;Cooper et al 2013a, b;Kaur et al 2020) refers to stones that have a special relevance in human culture. For example, the porphyries from Sweden (Wikström et al 2015); "Petit granit" and Lede stone from Belgium (Pereira et al 2015;De Kock et al 2015); slates from the Iberian peninsula (Cardenes et al 2015); granites such as Piedra Berroqueña, of Madrid (Spain) (Freire-Lista et al 2015a, b;Fort 2016, 2019a, b) and Rosa Beta granite from Italy (Careddu and Grillo 2015); Larvikites from Norway (Heldal et al 2015); gneisses such as Facoidal gneiss from Brazil (Castro et al 2021); marbles, such as the one from Carrara in Italy (Primavori 2015;Murru et al 2018), the white marbles of Brasília (Frascá et al 2020), Estremoz marbles from Portugal (Lopes and Martins 2015) and Macael marble from Spain (Navarro et al 2019); and limestones such Lioz limestone from Portugal (Silva 2019), Bath and Purbeck limestones from England (Marker 2015); Villamayor sandstone from Salamanca (NW of Spain) (García-Talegón et al 2015), and Sydney sandstone from Australia (Cooper et al 2015). These stones have been widely used and with them, important buildings have been built that have marked the history of humankind (Siegesmund et al 2014).…”

Pedras do patrimônio da IUGS: histórico e requisitos

“…Por serem pequenas janelas da história da Terra, também possuem potencial valor educacional como meio de divulgação da geologia, pois estão acessíveis à população das cidades e a quem as visita e, ainda, registra o desenvolvimento natural e cultural de localidades ou regiões, já que o uso de materiais pétreos locais sempre foi privilegiado por motivos de acesso e custo (De Wever et al, 2017). Um exemplo disso é o Gnaisse Facoidal, a rocha mais utilizada na construção do Rio de Janeiro até o século XX (Castro et al, 2021) e que dá forma aos famosos picos da sua paisagem, como o Pão de Açúcar, incluído na lista dos 100 primeiros geossítios mundiais da União Internacional de Ciências Geológicas (IUGS) (https://iugs-geoheritage.org/ geoheritage_sites/the-sugar-loaf-monolith-of-rio-de-janeiro/).…”