The Thorvaldsens Museum Archives

[...] Mr (S) Gibson however in a letter accompanying his design, apprised the committee that the marble of the valley of Callonata, of which he proposed to construct the edifice, possessed all the requisite durability to resist the effects of our climate. Callonata marble from its flinty quality being entirely impervious to humidity, induced Mr Nash to use it in constructing the triumphant arch in front of Buckingham Palace. The celebrated Thorwaldsen has also adopted it for the colossal statue of Christ and his Apostles, which decorate the pediment of the cathedral now in progress of erection at Copenhagen. [...]