Location of quarries of magnesian lime used as raw material of Roman plasters in western Lombardy (Italy)

Abstract

Lime as building material was widely diffused in Roman architecture of western Lombardy. The presence of magnesite (magnesium carbonate) was detected in painted plasters coming from roman sites of Milano: magnesite indicates the use of dolomite to make the lime. Dolomite rocks widely outcrop in the Lombard Prealps: light grey dolomites and dolomitic limestones (Dolomia del Salvatore, Ladinian-Anisian); grey dolomites, sometimes with cyclothemes (Dolomia Principale, Norian). There is no evidence of Roman lime quarries or kilns in this area; the Romans probably exploited the same dolomite outcrops, located along the eastern shore of lake Maggiore, where lime was produced from the Middle Ages onwards. The glacio-fluvial deposits of the middle course of the river Adda (cobbles, pebbles of siliceous limestone together with limestone and dolomite outcropping in the river basin) were another medieval and modern source of raw material, mainly to make a moderately hydraulic lime (called “calce forte”), but this kind of lime is lacking in Roman plasters.