Pískovce z Pražského hradu a okolí
Study of eleven pieces of quartz sandstones come from an archaeological collection of Prague´s Castle showed at least two different rocks provenances. Fine greenish - yellowish soft clayey sandstones, which contain also a small portion of calcite and glauconite was designated as „Zápy“ sandstones, which has a short durability, high porosity and low strength. The second groups of whitish - greyish coarser quartz sandstones with higher strength and a small content of kaolinite and illite comes probably from Nehvizdy - Vyšehořovice. Study of further sandstone samples gathered from other various Prague´s outcrops (Strahov, Střešovice, Prosek and Hloubětín) showed, that these soft clayey sandstones could not be used neither as a building material not as a architectural stone.