Red Marly Limestone

Red Marly Limetsone used in the Cattedrale di Santa Maria del Fiore.

Lithotype

Red Marly Limestone

Common names

Calcare Rosso, Marmo Rosso, Marna del Sugame, Rosso Montieri, Rosso di Monterantoli, Rosso di Monsummano

Rock Classification

Sedimentary rock

The Red Marly Limetsone outcrops in different provinces of the Tuscany region and mainly in the area of Florence (Greve), Pistoia (Munsummano), Grosseto (Montieri).

The material comes from the Scaglia Toscana Formation, part of the Tuscan Nappe Unit. The age ranges between the Low Cretaceous and the Paleogene. The formation consists of several members, including that of the “Marne del Sugame”, from which the lithotype historically used, comes. These latter are marly limestones showing a variable color, from dark red to gray-green. The thickness is difficult to be evaluated; in the less disturbed sequences the thickness is in the range between 20-30 meters and 80-100 meters.

This limestone, of ornamental effect, has been used both for indoors and outdoors, mainly in Tuscan religious architecture from the Renaissance to the XIX century. It was widely used in many monuments of Firenze: the external cladding of the lateral sides, the apses and the paving of the Cattedrale di Santa Maria del Fiore, the façades of the Basilica di Santa Maria Novella and Santa Croce.

The composition is mainly calcitic and clayey; iron oxides are also present.

MACROSCOPIC DESCRIPTION

The Red Marly Limestone displays a dark red color; it is a low-porosity, compact and polishable rock. Thin calcitic veins are common.

Macroscopic aspect of a Red Marly Limestone.

MICROSCOPIC DESCRIPTION

Due to the clay component and the presence of a hematitic pigment, the rock has a cloudy aspect. The microfossilferous content is abundant. Bioturbations and thin veins of calcite are frequent; these last differ from the surrounding mass for higher crystalline grain and for the lack of pigment.

Thin section micrograph of a Red Marly Limestone.