The Rosso Ammonitico Veronese, a Jurassic nodular limestone quarried since ancient times in S. Ambrogio di Valpolicella, Verona, Italy, has been characterized both in its minero-petrography and geochemistry. The same tests were carried out on decayed nodular limestone from Ca' d'Oro (early 15th century) in Venice. Geochemical investigations in particular are fundamental for the correct geographical collocation of the stone, proving for the Ca' d'Oro material a provenance other than the hypothesized one. Beside that, different patterns of deterioration have been identified, mainly due to the different environmental conditions: in the quarry and in the town of Venice, whose saline and polluted atmosphere plays an essential role. -- AATA