The Red Ammonitic Limestone outcrops in several provinces of the Tuscany region and mainly in the area of Pistoia (Monsummano), Livorno (Sassetta), Pisa (Avane) , Lucca (Collemandina), and Grosseto (Gerfalco).
The Red Ammonitic Limestone belongs to the Red Ammonitic Formation of the Tuscan Series (Lower Jurassic); the formation consists of calcareous layers, pink or gray-pink in colour, and calcareous layers showing reddish colour and a characteristic nodular appearance; thin levels of shales and marly siltites alternate with calcareous layers. The rock, containing ammonites and variable amount of hematitic pigment, is classified as a biomicrite.
The Red Ammonitic Limestone is a material of great ornamental effect, used in Tuscany, in interiors and exteriors, mainly in religious architecture since the Renaissance period, until the XIX century. It has been used, in Firenze, in external and internal claddings of very important churches such as the Cattedrale di Santa Maria del Fiore, the Basilica di Santa Croce and the Basilica di Santa Maria Novella.
Mainly calcitic in composition with small amount of iron oxides and traces of quartz and clay minerals.
The rock is red, stratified, compact, with low porosity; it is nodular in texture and contain fossils, mainly ammonites; stilolitic joints and veins of clearer color are also present.
The rock is constituted by a very fine-grained biomicrite containing variable amount of hematitic pigment and bioclasts, mainly ammonites. A peculiar characteristic is the presence of wide-sized calcite veins and stilolitic joints containing clay minerals, iron oxides and quartz crystals.