Thanks to its almost continuous outcrop area along the foothills, Sarnico sandstone is to be found practically everywhere in classical architecture and art, but also in agriculture and general civilian uses for technical and practical purposes. The connection between the extent of the outcrop and its wide use is not clear enough. The reader gets as far as "everywhere" still thinking you are talking about its occurrence in nature ("is to be found").
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enoonI do not believe that the sandstone is found practically everywhere in art. You want to contrast its use in art with its other uses, but the contrast as you have it is not strong enough for a "but".I'm going for "not only - but also". I'll also replace "practically everywhere" with "frequently".