The Origin of the Stone

The principal centres of limestone production in Continental Portugal are to be found in the Maciço Calcário Estremenho, amongst which SOLANCIS quarries. Find out about the origins of the limestone formation process in this region and understand why it presents some unique characteristics.

In Continental Portugal three great geological areas can be distinguished: the Ancient Massif (Maciço Antigo) the Meso-Cenozoic Shelves (Orlas Meso-Cenozóicas) and the Tejo and Sado Basins.

The Maciço Antigo is the oldest geological area and that which occupies the majority of the Portuguese territory. It is constituted by durable rock, amongst which slates, marbles, and, predominantly, granites.

The Orlas Meso-Cenozóicas are composed of the Orla Meso-Cenozóica Ocidental (Western Shelf), which extends from the coast from Espinho to the Serra da Arrábida, and the Orla Meso-Cenozóica Meridional (Southern Shelf) which occupies the Algarve coastline. Its formation is due to tectonic activity. Here thick series of limestone deposits are found, as well as sand and clay.

The Tejo and Sado basins were formed more recently and are the result of two gulfs which subdivide the Orla Meso-Cenozóica Ocidental. Here thick sequential deposits of marine and fluvial sediment from the bottom of the ocean appear. Predominantly the types of rock found are sandy, clay and limestone

Limestone formation

Limestone is a sedimentary rock which is constituted by it principle mineral calcite. It originates in a marine environment when it suffers a loss of carbon dioxide. In the process of replacing the levels of carbon dioxide, calcite is formed. Later limestone is formed, accumulating marine animal fossils (shells, corals, algae) and diverse sedimentary structures which reflect the existing environmental conditions. This depositing process can lend some important aesthetic features to the rock.

Maciço Calcário Estremenho

In Portugal limestone rock is principally found in the Orlas Meso-Cenozóicas. The principal centres of productions are in the Orla Meso-Cenozóica Ocidental, more specifically in the Maciço Calcário Estremenho. This mountainous region is approximately 800km² and its peculiar landscape is situated between Rio Maior, Tomar and Leiria.

Characteristics and varieties of limestone

The limestone extracted from the Maciço Calcário Estremenho are normally clear cream limestone, ranging from rough to fine grain with various disperse elements, amongst which, oolites (the size of a grain of sand), bioclasts (marine fossils), litoclasts (rock fragments), glutinated in a cement of translucid calcite crystals. This limestone is available in solid slabs.

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