Siltstone

**Petrology:** Siltstone is composed of clay and silty fraction cemented by carbonates. A significant proportion of silica derived from needles of marine sponges positively affects the rock strength. Siltstone is whitish to yellow-grey sand colour.

**Genesis:** Siltstone is a typical marine sediment, which was widely used as building material mainly in the Romanesque architecture in Prague.

## Keywords
stone, sediment, rock