Some types of sedimentary rocks include: Siltstone, which is made of a smooth rock with very fine angular grains. Sandstone forms when grains of sand become cemented together. Clay is also a sedimentary rock, it is fine-grained and may become malleable, which means capable of being shaped or formed when wet. Tufa forms when cool, calcite-rich springs evaporate. Conglomerate contains rounded beach pebbles and other small stones. Shale is a rock that forms from hardened particles of clay. Finally, limestone's main ingredient is calcite, which is calcium carbonate.