Zandobbio (pink dolomite)
— Ceppo di Grè/Ceppo Poltragno (conglomerate)
— Pietra di Chiampo (pink limestone)
— Pietra di Aurisina (grey limestone)
— Pietra di Finale (pink to yellow limestone)
— Rosso Amiata (red limestone)
— Portasanta di Caldana (red limestone)
— Travertino di Rapolano (light carbonate deposit)
METAMORPHIC
— Verde Alpi (green, white veined ophicalcite)
— Rosso di Lèvanto (red or green ophicalcite)
— Verde Roja (green clayey schist).
MARBLE
— Marmo di Valle Strona (grey, veined)
— Marmo di Lasa (white, veined)
— Fior di pesco carnico (grey, pink spots)
— Calacatta, Cipollino (white or green, veined)
Each stone is discussed in order to enhance: macroscopic and microscopic features together with decay phenomena caused by weathering agents (Biondelli 2004b); geological settings (Ispra 1976, Ispra 2012); quarry sites (Peverelli and Squarzina 1939, Pieri 1966); use and application in architecture, mainly in Milan, but also in other important cities (Grandi 1980, Gramigna 2001, Pierini 2017).
Rosso Pantheon
Igneous rock (granite). Colour: dark red, scattered of light grey spots. Minerals: quartz, potash feldspar and plagioclase. Decay morphologies: scaling. Geology: “Serie del Canavese” (Permian-Triassic) including red and grey granites barren of micas. Quarry: few kilometres west of Valperga (Cuorgnè, Canavese, Torino province). Use: mainly polished slabs for façade cladding of residential and public buildings (Palazzo INA, portals and cladding in the porch, P. Portaluppi, 1936, Milan; Palazzo del Popolo d’Italia, balcony, G. Muzio 1938/42, Milan).
Sienite della Balma
Igneous rock (syenite). Colour: violet with black spots. Minerals: potash feldspar (orthoclase), plagioclase, amphibole (hornblende), biotite, piroxene (augite), quartz. Decay morphologies: scaling. Geology: Valle Cervo pluton (late-alpine, Oligocene) of the “Sesia-Lanzo Zone” (meta-morphic rocks, mainly micaschists). Quarry: near the village of Balma (valle del Cervo, Biella province). Use: polished slabs for cladding of residential and public buildings (Palazzo delle Colonne, façade made of very thick slabs with point chiseled surface in a T-shaped building with a porch of ten couples of shafts of Granito di Santo Stefano (Sardinia), G. Muzio – G. Greppi 1940, Milan).
Diorite nera di Anzola
The commercial name refers to a wrong petrographic classification: this is a igneous coarse grained rock (amphibole gabbro). Colour: black with some light grey spots. Minerals: plagioclase, hornblende. Decay morphologies: scaling. Geology: “Dioritico – kinzigitica” forma-tion of the “Ivrea-Verbano Zone”. Quarry: near the village of Anzola (val d’Ossola, Verbano province). Use: squared blocks and slabs (Banca Popolare, framework of openings, G. Greppi 1931, Milan); another use was for funerary purposes (Mausoleo Cadorna, M. Piacentini 1932, Pallanza; Cemeteries, Milan).
A stone, of the same colour but unlike origin (migmatite, Gneiss Valcondria), was quarried in val Chiavenna (Sondrio) and used in buildings.
Porfido monumentale
Igneous rock (rhyolitic ignimbrite). Colour: purple to dark red showing clear phenocrysts and some elliptic coarse-grained patches. Minerals: quartz and 43plagioclase. Decay morphologies: scaling. Geology: “Vulcaniti di Auccia” forma-tion (lower Permian). Quarry: near the pass of “Croce Domini” (Bienno, val Camonica – val Trompia, Brescia province). Use: thick slabs for cladding or slabs for flooring (Palazzo delle Colonne, polished thick slabs deeply carved by Giacomo Manzù to represent the “coats of arms” of the Lombard provinces).
Pietra di Zandobbio
Carbonate rock (dolomite). Colour: light pink tending to whitish with fine cracks featuring a typical network. Mineral: dolomite. Decay morphologies: surface erosion with widening of the crack network; sulphate skin formation. Geology: “Dolomia di Zandobbio” formation (Hettangian - Rhaetian) of the sedimentary series of Southern Alps. Quarry: near the villages of Zandobbio (Bergamo proince). Use: firstly during the Renaissance period (i. e. Cappella Colleoni, 1472–76; Biblioteca Angelo Maj, early 17th century); later (20th century) greatly imple-mented (Palazzo Littorio, cladding made of slabs with sawed face, A. Bergonzo 1940, Bergamo) and it was also spread in Milan for residential and public building.
Ceppo di Grè/Ceppo Poltragno
Clastic rock (diamictite with ocraceous matrix and calcite cement, clasts with angular corners). Colour: grey with some yellowish hues. Mineral: clasts of Dolomia principale (Haupt dolomit), size from 0.05 to 1.0 m. Decay morphologies: roughening on clasts and matrix, soot deposition on cavities, sulphate skins formation. Geology: “Complesso di Poltragno”, subdivided in two units (Unità di Poltragno and Unità di Gré), including slope deposits and alluvial deposits (lower and middle Pleistocene). Quarry: near Castro (Bergamo province), on the mountain rising above the north-western shore of lake Iseo. Use: slabs with sawed face for cladding of residential and public buildings (Casa dei Giornalisti, G. Muzio 1936, Milan; Palazzo Vittoria, E. Frisia 1935, Milan). Besides, this conglomerate is employed today (i. e. the façade cladding on the new building of Università Bocconi, Grafton architects 2008, Milan).
Pietra di Chiampo
Organic carbonate rock (shell limestone, biomicrite – packstone) wiht different varieties according to the colour and the texture (Rosa, Perla, Mandorlato, Paglierino). Colour: white to yellow to pink ground scattered with small light spots (shells of Foraminifera). Mineral: calcite. Decay morphologies: surface erosion, sulphate skin formation. Geology: “Calcari nummulitici” formation (Eocene) of the sedimentary series of the Western Venetia. Quarry: few kilometres near Chiampo, a village of the same valley (Vicenza province); limestone in alternating with basalt. Use: slabs for cladding (Palazzo Popolo d’Italia) or for flooring and stairs (Intendenza di Finanza, Genio Civile 1935, Milan).
Pietra di Aurisina
Organic carbonate rock (limestone, biosparite-wackestone) with different varieties according to the texture (Fiorito, Granitello). Colour: grey with evidence of shells of Bivalves (Rudistae). Mineral: calcite. Decay morphologies: surface erosion, sulphate skin formation. Geology: “Calcare di Aurisina” formation (upper Creta-ceous) of the Karst of Trieste. Quarry: near Aurisina (Nabrežina) in the north-western part of Karst (Trieste province). Use: early uses are documented in Roman architecture of north-eastern Italy and also in Milan (funerary stelae and blocks of urban walls); nevertheless
